UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


UNIVERSITY  of  CALIFORNIA 

LOS  ANGELES 
LIBRARY 


INTRODUCTION 


RARER    ELEMENTS. 


BY 


PHILIP  E.   BROWNING,   PH.D., 

Attiftant  Pro/estor  of  Chimittry,  Ktnt  Cktmical  Laboratory, 
Yalt  Univtrtitf. 


FOURTH  EDITION,   THOROUGHLY  REVISED. 
SECOND    IMPRESSION,   CORRECTED 


NEW  YORK 

JOHN  WILEY  &  SONS,  INC. 

LONDON:    CHAPMAN  &  HALL,  LIMITED 

1919 

123206 


COPTEIQHT,  1903,  1908,  1912,  1917, 

BY 

PHILIP  E.  BROWNING. 


PRESS  OF 

k  CO. 
BOOK   MANUFACTURERS 


I  17 

cob< 


PREFACE   TO  THE   FOURTH  EDITION. 


IN  attempting  to  bring  this  work  up  to  date  for  a  new 
|      edition  the  author  has  made  numerous  changes  and  addi- 
V      tions  throughout. 

The  chapter  on  Radio-Elements  has  been  thoroughly 
revised  by  Professor  B.  B.  Boltwood,  who  contributed  it 
originally  to  the  second  edition.     Professor  H.   S.   Uhler, 
who  aided  in  the  selection  of  certain  spectroscopic  material 
for  the  third  edition,  has  furnished  a  plate  showing  the 
spectrum  of  gallium  and  also  the  spectra  of  certain  gallium 
S"      and  indium  products  prepared  in  collaboration  with  the 
4\^.    author.     To  both  of  these  colleagues  the  author  acknowl- 
edges his  indebtedness. 

The  section  dealing  with  the  rare  earths  has  been  re- 
arranged in  accordance  with  recent  researches  in  that  field. 
«\,      The  discovery  of  gallium,  indium,  and  germanium  in  appre- 
^w     ciable   amounts   in   certain   of   our   American   commercial 
mineral  products  has  furnished  material  for  a  wider  study  of 
these  elements,  and  has  made  desirable  a  more  extended  de- 
scription of  their  chemical  behavior.      The  treatment  of  the 
subject  of  qualitative  separation  has  been  made  fuller  by 
^      the  introduction  of  certain  alternative  methods;    and  some 
\J      of  the  newer  technical  applications  of  the  rarer  elements 
*      have  been  noted.     A  table  has  been  prepared  to  show  the 
chief  associates  of  these  elements,  and  so  to  indicate  the 
major  analytical  problems  which  face  the  chemist  inter- 
ested in  them. 

Special  attention  has  been  given  to  the  revision  of  the 
experimental  work,  which  now  consists  of  about  two  hun- 

iii 


fr  PREFACE. 

dred  experiments.  Included  in  these  are  adaptations,  suit- 
able for, the  laboratory,  of  processes  by  means  of  which 
compounds  of  practically  all  the  rarer  elements  may  be 
obtained  from  available  minerals  or  from  commercial 
by-products.  A  careful  study  of  the  experiments  will 
accomplish  the  main  purpose  of  the  book. 

The  author  wishes  to  reiterate  the  statement  made  in 
former  prefaces  that  this  little  work  is  intended  not  to 
treat  exhaustively  the  subject  of  the  rarer  elements,  but 
rather  to  serve  as  an  introduction  to  the  study  of  an  inter- 
esting group  which  the  chemist  in  the  inorganic  field  cannot 
afford  to  neglect. 

NEW  HAVEN,  CONN.,  January,  1917. 


PREFACE  TO  FIRST   EDITION. 


THIS  small  volume,  prepared  from  material  used  by  the 
author  in  a  short  lecture  course  given  at  Yale  University, 
is  intended  to  serve  as  a  convenient  handbook  in  the  intro- 
ductory study  of  the  rarer  elements ;  that  is,  of  those 
elements  which  are  not  always  taken  up  in  a  general  course 
in  chemistry.  No  attempt  has  been  made  to  treat  any  part 
of  the  subject  exhaustively,  but  enough  references  have 
been  given  to  furnish  a  point  of  departure  for  the  student 
who  wishes  to  investigate  for  himself.  Experimental  work 
has  been  included  except  in  the  case  of  those  elements  which 
are  unavailable,  either  because  of  their  scarcity  or  because 
of  the  difficulty  of  isolating  them. 

The  author  has  drawn  freely  upon  chemical  journals  and 
standard  general  works.  In  his  treatment  of  the  rare  earths 
he  has  made  especial  use  of  Herzfeld  and  Korn's  Chemie 
der  seltenen  Erden  and  Truchot's  Les  Terres  Rares,  works 
which  he  gladly  recommends.  He  gratefully  acknowledges 
the  valuable  assistance  of  his  wife  in  preparing  this  ma- 
terial for  the  press. 

NEW  HAVEN   CONN.,  April,  1903. 


TABLE   OF   CONTENTS. 


CHAPTER  PAOB 

I.  THE  ALKALIES i 

II.  BERYLLIUM 17 

III.  THE  RADIO -ELEMENTS 25 

IV.  THE  RARE  EARTHS 35 

V.  GALLIUM,  INDIUM,  THALLIUM 83 

VI.  TITANIUM,  GERMANIUM 97 

VII.  VANADIUM,  NIOBIUM,  TANTALUM 107 

VIII.  MOLYBDENUM,  TUNGSTEN,  URANIUM 125 

IX.  SELENIUM,  TELLURIUM 144 

X.  THE  PLATINUM  METALS,  GOLD 161 

XI.  THE  RARE  GASES  OF  THE  ATMOSPHERE 191 

XII.  TECHNICAL  APPLICATIONS 197 

XIII.  QUALITATIVE  SEPARATION 207 

XIV.  SPECTROSCOPIC  TABLES 227 

REVIEW  QUESTIONS 235 

MINERALS  AND  REAGENTS  USED  IN  THE  STUDY  OF  THE  RARER  MINERALS  249 

PUBLISHED  WORKS  OF  PHILIP  E.  BROWNING 251 

INDEX 2S7 

vii 


INDEXES  TO  THE   LITERATURE   OF  CERTAIN 
ELEMENTS. 


Beryllium,  The  Chemistry  and  Literature  of  (1798-1908);  Parsons- 
Easton,  Penn.  The  Chemical  Publishing  Co. 

Cerium,  Index  to  the  Literature  of  (1751-1894);  Magee.  Smithsonian 
Misc.  Coll.  (1895),  No.  971. 

Columbium,  Index  to  the  Literature  of  (1801-1887);  Traphagen. 
Smithsonian  Misc.  Coll.  (1888),  No.  663. 

Didymium,  Index  to  the  Literature  of  (1842-1893);  Langmuir.  Smith- 
sonian Misc.  Coll.  (1894),  No.  972. 

Gallium,  Index  to  the  Literature  of  (1876-1903);  Browning.  Smith- 
sonian Misc.  Coll.  (1904),  No.  1543. 

Germanium,  Index  to  the  Literature  of  (1886-1903) ;  Browning.  Smith- 
sonian Misc.  Coll.  (1904),  No.  1544. 

Indium,  Index  to  the  Literature  of  (1863-1903);  Browning.  Smithson- 
ian Misc.  Coll.  (i905j,  No.  1571. 

Lanthanum,  Index  to  the  Literature  of  (1839-1894);  Magee.  Smith- 
sonian Misc.  Coll.  (1895),  No.  971. 

Niobium  or  Columbium,  vid.  Columbium. 

Platinum  Metals,  Bibliography  of  (1748-1897);  Howe.  Smithsonian 
Misc.  Coll.  (1897),  No.  1084. 

Rare  Earths,  Bibliographic  der  seltenen  Erden;  Meyer.  Hamburg. 
Leopold  Voss,  1905.  Also,  Catalogue  of  Theses,  C.  Richard' 
Bohm.  Zeitsch.  angew.  Chem.  (1912)  xxv.  758.  j 

Thallium,  Index  to  the  Literature  of  (1861-1896);  Doan.  Smith- 
sonian Misc.  Coll.  (1899),  No.  1171. 

a. 


X         INDEXES   TO    THE  LITERATURE  CF  CERTAIN  ELEMENTS. 

Thorium,  Index  to  the  Literature  of  (1817-1902);  Jouet.     Smithsonian 

Misc.  Coll.  (1903),  No.  1374. 
Titanium,  Index  to  the  Literature  of  (1783-1876);  Hallock.     Annals  of 

the  N.  Y.  Academy  of  Sciences  (1876),  i,  53. 
Uranium,  Index  to  the  Literature  of  (i  789-1885) ;  Bolton.     Smithsonian 

Report  for  1885,  Part  i,  915. 
Vanadium,  Index  to  the  Literature  of  (1801-1877);  Rockwell.     Annals 

of  the  N.  Y.  Academy  of  Sciences  (1879),  i,  133. 
Vanadins,  Die  Literatur  des  (1804-1905);  Prandtl.     Hamburg,  Leopold 

Voss,  1906. 
Zirconium,  Index  to  the  Literature  of   (1789-1898);  Langmuir  and 

Baskerville.     Smithsonian  Misc.  Coll.  (1899),  No.  1173. 

Attention  is  called  also  to  the  following  monographs: 

Die  Physikalisch-Chemischen  Eigenschaften  des  metallischen  Selens; 
Marc.  Pub.  by  Leopold  Voss,  Hamburg,  1907. 

Die  Chemie  des  Thoriums;  Koppel.  Sammlung  chemischer  Vortrage, 
Band  VI.  Pub.  by  Ferd.  Enke,  Stuttgart,  1901. 

Studien  fiber  das  Tellur;  Gutbier.  Pub.  by  C.  L.  Hirschfeld,  Leipzig, 
1902. 

La  Chimie  de  L'Uranium  (1872-1902);  Oechsner  de  Coninck.  Pub. 
by  Masson  et  Cie.,  Paris,  1902. 

The  Analytical  Chemistry  of  Uranium;  H.  Brearley.  Pub.  by  Long- 
mans, Green  &  Co.,  London  and  New  York,  1903. 

Die  analytische  Chemie  des  Vanadins;  Valerian  von  Klecki.  Pub.  by 
Leopold  Voss,  Hamburg,  1894. 

Le  Vanadium;  P.  Nicolardot.     Pub.  by  Masson  et  Cie.,  Paris. 

Das  Vanadin  und  seine  Verbindungen;  Fritz  Ephraim.  Pub.  by  Ferdi- 
nand Enke,  Stuttgart,  1904. 

The  Occurrence,  Chemistry,  Metallurgy,  and  Uses  of  Tungsten. 
Runner  and  Hartmann,  South  Dakota  School  of  Mines,  Rapid 
City,  S.  D.  Bull.  No.  12. 


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THE   RARER  ELEMENTS 

CHAPTER  I. 
THE  ALKALIES. 
LITHIUM,  Li,  6.94. 

Discovery.  In  1817  Arfvedson,  working  in  Berzelius's 
laboratory  upon  a  petalite  from  Uto,  Sweden,  discovered 
an  alkali  which  he  found  to  differ  from  those  already  known 
in  the  following  particulars:  (i)  in  the  low  fusing  points 
of  the  chloride  and  sulphate;  (2)  in  the  hydroscopic  char- 
acter of  the  chloride ;  and  (3)  in  the  insolubility  of  the  car- 
bonate. In  his  analysis  of  the  mineral  it  had  remained 
associated  with  sodium,  not  being  precipitated  by  tartaric 
acid.  To  the  newly  discovered  element  the  name  Lithium 
was  given,  from  A/0o?,  stone,  because  it  differed  from 
sodium  and  potassium  in  having  a  mineral  rather  than 
a  vegetable  origin  (Ann.  der  Phys.  u.  Chem.  (1818),  xxix, 
229;  Ann.  Chim.  Phys.  [2]  x,  82).  It  has  since  been  found, 
however,  not  only  in  the  mineral  kingdom,  but  in  the 
vegetable  and  animal  kingdoms  also. 

Occurrence.     Lithium  is  found  combined  as  follows: 

(i)  In  minerals: 

Petalite,          LiAl(Si205)2,  contains  2-5%*  Li20. 

Spodumene^  LiAl(SiO3)2,  "        4-8%       " 

Lepidolite,       R3Al(SiO3)3,                            "        4-6%       " 
Zinnwaldite,  (K,Li)3FeAl3Si6O]6(OH,F)2,  "        3-4%       " 
Cryolithionite,  Li3Na3Al2Fi2,                      "        5-6%  Li 
Cryophyllite,  complex  silicate,   vid.   Zinnwaldite,  contains 
4-5%  LiaO. 

*  In  the  tabulation  of  percentages  the  nearest  whole  numbers  have  generally 
been  used  in  this  book. 

j1  The  more  important  mineral  sources  are  indicated  by  italics. 


2  THE  RARER  ELEMENTS. 

Irvingite,  complex  silicate,  contains  4-5%  Li2O. 
Polylithionite,  complex  silicates,  vid.  Zinnwaldite,  contains 

about  9%  Li2O. 

Beryl,  Be^l^SiO,),,      contains  0-1%    Lif>. 

Tnphylite,      Li(Fe,Mn)PO4>  8-9% 

Lithiophilite,  Li(Mn,Fe)PO4,  8-9% 

Amblygonite,  Li(AlF)PO4,  "         8-10%    ' 

Natramblygonite,  NaAl(OH)PO4,  "       3~4% 
Sicklerite,  FesOs^MnO^CVaCLiH^O,  cent's  3.8%  Li2O. 


Small  amounts  of  lithium  are  found  also  in  some  varieties  of 
tourmaline,  in  epidote,muscovite,orthoclase,and  psilomelane. 

(2)  In  certain  mineral  waters,  among  which  are  Dtirk- 
heim,    Kissingen,    Baden-Baden,    Bilin,    Assmannshausen, 
Tarasp,  Kreuznach,  Salzschlirf,  Aachen,  Selters,  Wildbad, 
Ems,    Homburg,    Karlsbad,    Marienbad,    Egger-Franzen- 
bad,  Wheal  Clifford,  Bad  Orb,  Sciacca,  Salsomaggiore. 

(3)  In    seaweed,    tobacco,    cacao,    coffee,    and   sugar- 
cane;  in  milk,  human  blood,  and  muscular  tissue;   in  me- 
teorites, soils,*  and  sea-water. 

Extraction.  Lithium  may  be  extracted  from  minerals 
by  the  following  methods: 

(1)  From  triphylite  or  lithiophilite.    The  coarsely  ground 
mineral  is  dissolved  in  hydrochloric  acid  to  which  nitric 
acid  is  gradually  added,  and  the  solution  obtained  is  treated 
with  a  sufficient  amount  of  ferric  chloride  to  unite  with  all 
the  phosphoric  acid  present.     This  solution  is  evaporated 
to  dryness  and  the  residue  is  extracted  with  hot  water. 
The  extract  thus  obtained  is  treated  with  barium  sulphide, 
to  remove  the  manganese  and  the  last  traces  of  iron.     The 
barium  is  removed  by  sulphuric  acid,  and  the  filtrate  is 
evaporated  with  oxalic   acid  and  ignited.      The   alkalie? 
remain  as  carbonates  (Muller). 

Lithium  may  be  separated  from  the  other  alkalies  b} 
treating  the  mixed  carbonates  with  water,  lithium  carbonate 
being  comparatively  insoluble. 

(2)  From  lepidolite  (or  any  other  silicate}.     The  mineral  is 

*  Vid.  Steinkoenig,  J.  Ind.  Eng.  Chem.  vn,  425  (1915). 


LITHIUM.  3 

melted  at  /ed  heat  in  a  crucible,  the  melted  mass  is  cooled 
rapidly  in  water  and  pulverized.  Sufficient  water  is  added 
to  give  the  material  the  consistency  of  paste.  Hydrochloric 
acid  of  specific  gravity  1.2,  equal  in  weight  to  the  weight 
of  the  mineral  taken,  is  gradually  added,  with  stirring. 
The  mass  is  allowed  to  stand  for  twenty-four  hours.  It  is 
then  heated  again  to  about  100°  C.,  with  stirring,  and  a 
second  portion  of  acid  equal  to  the  first  is  added.  Upon 
several  hours'  heating  the  silica  separates  in  the  form  of 
powder,  and  after  treatment  with  nitric  acid  to  oxidize 
the  iron,  the  soluble  material  is  separated  by  filtration  from 
the  silica.  The  filtrate  is  heated  to  the  boiling-point  and 
treated  with  sodium  carbonate,  which  precipitates  iron, 
aluminum,  calcium,  magnesium,  manganese,  etc.  These 
are  removed  by  filtration,  and  the  liquid  is  evaporated  to 
a  small  volume  and  filtered  again  if  necessary.  Lithium 
carbonate  is  precipitated  by  more  sodium  carbonate 
(Schrotter). 

The  Element.  A.  Preparation.  Elementary  lithium  may 
be  obtained  (i)  by  subjecting  the  fused  chloride  or  bromide' 
to  electrolysis;  (2)  by  heating  a  mixture  of  elementary 
calcium  and  lithium  chloride  in  the  presence  of  hydrogen 
(Hackspill). 

B.  Properties.  Lithium  is  a  metallic  element  which  has 
a  silvery-white  luster  and  which  oxidizes  in  the  air,  though 
more  slowly  than  potassium  and  sodium.  It  decomposes 
water  at  ordinary  temperatures,  and  is  light  enough  to 
float  in  petroleum.  Its  melting-point  is  183°  C. ;  its  specific 
gravity  is  0.59. 

Compounds.  A.  Typical  forms.  The  following  are 
typical  compounds  of  lithium: 

Oxides,  Li2O;  Li2O2.      85.45. 

Hydroxide,  LiOH. 

Carbonate,  Li2CO8. 

Chloride,  LiCl. 

Chlorate,  LiCIO,  +  o. 5H2O. 


THE  R4RER  ELEMENTS. 


Perchlorate, 

Bromide,  LiBr. 

Bromate,  LiBrO3. 

Iodide,  LiI  +  3H2O. 

lodate,  LiIO3  +  o.5H2O. 

Periodate,  LiIO4. 

Fluorides,  LiF;  LiF-HF. 

Nitride,  LiNs. 

Nitrite,  LiNO2  +  o.5H2O. 

Nitrate,  LiNO3. 

Sulphide,  Li2S. 

Sulphite,  Li2S03. 

Sulphates,  Li2SO4;  KLiSO4;  NaLiSO4;  etc. 

Phosphates,  LiH2PO4;  Li3PO4  +  o.5H2O;  Li4P2O7. 

Carbide,  Li2C2. 

Silicofluoride, 


B.  Characteristics.  Most  of  the  salts  of  lithium  are 
easily  soluble  in  water;  the  principal  exceptions  are  the 
carbonate,  the  phosphate,  and  the  fluoride,  which  are 
difficultly  soluble.  Lithium  resembles  sodium  more  closely 
than  it  resembles  the  other  alkalies,  in  that  it  does  not 
form  an  insoluble  chloroplatinate,  nor  a  series  of  alums. 
The  nitrate  and  the  chloride  are  soluble  in  alcohol.  The 
compounds  of  lithium  color  the  flame  brilliant  crimson. 

Estimation.  Lithium  is  usually  weighed  as  the  sul- 
phate or  chloride. 

Separation.  Lithium  may  be  separated  from  the  other 
members  of  the  alkali  group  (i)  by  the  ready  solubility  of  its 
chloride  in  amyl  alcohol  (Gooch,  Amer.  Chem.  Jour,  ix,  33)  ; 
(2)  by  the  solvent  action  of  absolute  ethyl  alcohol  upon 
the  chloride;*  (3)  by  the  insolubility  of  the  phosphate  in  the 
presence  of  ammonia  and  ethyl  alcohol  (Benedict  Amer. 

*  At  25°  C.,  ioo  grm.  ethyl  alcohol  dissolves  amyl  alcohol  d  ssolves 
Licl  .............           25.8    grm.  9.03    grm. 

NaC1  ............  0.065   "  0.002      ' 

£C1.  ............  0.02     '  0.0008   ' 

RbC1  ............  0-078   "  0.0025    ' 


EXPERIMENTAL   WORK  ON  LITHIUM.  5 

Chem.  Jour,  xxxn,  480) ;  (4)  by  the  comparative  insolubility 
of  the  carbonate;  (5)  by  the  solubility  of  the  fluosilicate 
(Reichard,  Chem.  Ztg.  xxix,  861);  (6)  by  the  solubility  of 
the  chloride  in  primary  isobutyl  alcohol  (Winkler,  Ztschr. 
f.  anal.  Chem.  LII,  628) ;  (7)  by  the  solubility  of  the  chloride 
inpyridine  (Kahlenberg,  Jour.  Amer.  Chem.  Soc.  xxiv,  401). 

EXPERIMENTAL  WORK  ON  LITHIUM. 

Experiment  i.  Extraction  of  lithium  salts  from  tri- 
phylite  or  lithiophilite.  Dissolve  25  to  50  grm.  of  finely 
powdered  mineral  in  common  hydrochloric  acid,  add 
sufficient  nitric  acid  to  oxidize  the  iron,  and  enough  ferric 
chloride  to  combine  with  all  the  phosphoric  acid  present. 
Evaporate  to  dryness  and  extract  with  hot  water.  Treat 
the  extract  with  barium  hydroxide  in  slight  excess.  Filter, 
add  sulphuric  acid  to  complete  precipitation  of  barium 
sulphate,  and  filter  again.  Convert  the  sulphates  present 
into  carbonates  by  the  careful  addition  of  barium  carbonate, 
filter,  acidify  the  filtrate  with  hydrochloric  acid,  evaporate 
to  dryness,  and  extract  the  lithium  chloride  with  alcohol. 

(Lithium  salts  may  be  extracted  also  from  the  mother- 
liquor  after  the  extraction  of  caesium  and  rubidium  salts 
from  lepidolite.  The  liquor  is  treated  with  barium  car- 
bonate in  excess  and  is  then  boiled  and  filtered.  The 
filtrate  is  acidified  with  hydrochloric  acid,  evaporated  to 
dryness,  and  extracted  with  alcohol.) 

Experiment  2.  Precipitation  of  lithium  phosphate 
(LiaPO^  and  lithium  fluoride  (LiF).  (a)  To  a  solution 
of  a  lithium  salt  add  sodium  phosphate  in  solution.  (6) 
Try  similarly  the  action  of  sodium  fluoride. 

Experiment  3.  Precipitation  of  lithium  carbonate 
(Li2CO3).  To  a  few  drops  of  a  concentrated  solution  of 
a  lithium  salt  add  sodium  carbonate  in  solution. 

Experiment  4.  Solvent  action  of  alcohol  upon  lithium 
salts.  Try  the  action  of  ethyl  or  amyl  alcohol  upon  a 
little  dry  lithium  nitrate  or  chloride. 


6  THE  RARER  ELEMENTS. 

Experiment  5.  Flame  and  spectroscopic  tests  for  lithium. 
(a)  Dip  a  platinum  wire  into  a  solution  of  a  lithium  salt  and 
hold  in  a  Bunsen  flame.  Note  the  color. 

(6)  Observe  the  lithium  flame  by  means  of  the  spectro- 
scope. Note  the  bright  crimson  line  between  the  potas- 
sium and  sodium  lines. 

Experiment  6.  Negative  tests  of  lithium  salts.  Note 
that  hydrogen  sulphide,  ammonium  hydroxide,  ammonium 
carbonate  acting  upon  dilute  solutions,  chloroplatinic  acid, 
and  sodium  cobaltic  nitrite  give  no  precipitate  with  lithium 
salts. 


RUBIDIUM,  Rb,   85.45. 

Discovery.  Rubidium  was  discovered  by  Bunsen 
and  Kirchhoff  in  1861,  by  means  of  the  spectroscope,  in 
the  course  of  some  work  upon  a  lepidolite  from  Saxony 
(J.  B.  (1861),  173;  Chem.  News  in,  357).  The  alkaline 
salts  had  been  separated  by  the  usual  methods  and  pre- 
cipitated with  platinic  chloride.  The  precipitate,  when 
examined  with  the  spectroscope,  showed  at  first  only  the 
potassium  lines.  When  it  had  been  boiled  repeatedly 
with  water,  however,  the  residue  gave  two  violet  lines 
situated  between  the  strontium  blue  line  and  the  potas- 
sium violet  line  at  the  extreme  right  of  the  spectrum. 
These  increased  in  strength  as  the  boiling  continued,  and 
with  them  appeared  several  other  lines,  among  which 
were  two  almost  coincident  with  the  potassium  red  line  (a) 
at  the  extreme  left.  These  lines,  observed  for  the  first 
time,  marked  the  discovery  of  an  element ;  because  of  their 
color  Bunsen  gave  it  the  name  Rubidium,  from  the  Latin 
rubidus,  the  deepest  red. 

Occurrence.  Rubidium,  like  caesium,  is  widely  distrib- 
uted, but  in  very  small  quantities.  It  is  found 


RUBIDIUM. 
(i)  In  minerals: 


Lepidolite,       R^AlCSiO,),,        contains  0.7-3.0%  Rb2O. 

Leucite,  KAl(SiO3)2,  "         traces 

Spodumene,    LiAl(SiO3)2, 

Triphylite,       Li(Fe,Mn)PO4, 

Lithiophilite,  Li(Mn,Fe)PO4, 

Carnallite,       KMgCl3-6H2O, 

Mica  and  orthoclase  contain          "  " 

Some  microclines  2.3 

(2)  In  certain  mineral  waters,   among  which  are  the 
following  :    Ungemach,  Ems,  Kissingen,  Nauheim,  Selters, 
Vichy,  Wildbad,  Kochbrunnen  (Wiesbaden),  Diirkheim. 

(3)  In  beet-root,  many  samples  of  tobacco,  some  coffee  and 
tea,  ash  of  oak  and  beech,  crude  cream  of  tartar,  potashes, 
and  mother-liquor  from  the  Stassfurt  potassium  salt  works. 

Extraction.  Rubidium  may  be  extracted  with  caesium 
from  lepidolite  (vid.  Extraction  of  Caesium). 

The  Element.  A.  Preparation.  Elementary  rubidium 
may  be  obtained  (i)  by  heating  the  charred  tartrates  to  a 
white  heat  (Bunsen)  ;  (2)  by  reducing  the  hydroxide  or  the 
carbonate  with  magnesium  (Winkler,  Ber.  Dtsch.  chem. 
Ges.  xxin,  51)  ;  (3)  by  reducing  the  hydroxide  with  alumi- 
num (Beketoff);  (4)  by  heating  the  chloride  with  calcium 
(vid.  Lithium).- 

B.  Properties.  Rubidium  is  a  soft  white  metal  which 
melts  at  38°  C.  It  takes  fire  in  the  air,  burning  to  the 
oxide.  It  decomposes  water.  Its  specific  gravity  is  1.52. 

Compounds.      A.    Typical  forms.      The    following   are 
typical  compounds  of  rubidium  : 
Oxides,  Rb20;  Rb202;  Rb203;  Rb204. 
Hydroxide,  RbOH. 
Carbonates,  Rb2CO3;  RbHC03. 
Chloride,  RbCl. 
Double  chlorides,  HgCl2-2RbCl;  2PbCl2-RbCl;  BiCl3-6RbCl; 


g  THE  RARER   ELEMENTS. 

CdCU-aRbd;          2AsCl3-3RbCl;          3SbCl3.5RbCl; 

MnCl2-2RbCl+2H20;     ZnCl2-2RbCl;   MgCl2 •  RbCl  + 

6H20;  AuCl3.RbCl;  TeCl4.2RbCl;  TlCl^RbCl+H.O; 

and  many  others. 
Chlorate,  RbClO3. 
Perchlorate,  RbC104. 
Bromides,  RbBr;  RbBr3. 

Double  bromides,  2PbBr2-RbBr;  2AsBr3-3RbBr;  2SbBr3- 
3RbBr  ;AuBr3  •  RbBr  ;TeBr4  •  2RbBr  ;TlBr3  -3RbBr  +  H2O. 
Iodides,  Rbl;  RbI3;  and  others. 
Double  iodides,  AgI-2RbI;  PbI2-RbI  +  2H2O;  2AsI3-3RbI; 

2SbI3  •  3RbI ;  TeI4  •  2RbI ;  T1I3  •  Rbl  +  2H2O. 
lodates,  RbI03;  RbIO3-HIO3;  RbIO3-2HIO3. 
Nitride,  RbN3. 

Nitrates,  RbN03;  3RbNO3-Co(NO3)3  +  H2O. 
Cyanide,  RbCN. 

Sulphates,  Rb2S04;  RbHSO4;  Rb2S2O7;  Rb2O-8SO3. 
Alums,          RbAl(S04)2+  i2H20 ;          RbFe(SO4)2  +  i2H2O; 

RbCr(S04)2  + 1 2H20 ;    Rb2SO4  •  Ti2O3  -  3SO3  +  24H2O. 
Chloroplatinate,  Rb2PtCl6. 
Silicofluoride,  Rb?SiF6. 

B.  Characteristics.  The  rubidium  compounds  are  soluble, 
and  similar  to  those  of  potassium  and  caesium  (vid.  Caesium) . 
Among  the  important  insoluble  salts  are  the  perchlorate 
(RbClO4),  the  silicofluoride  (Rb2SiF6),  the  chloroplati- 
nate  (Rb2PtCl6),  the  bitartrate  (RbHO2C4H4O4),  the  alums 
(RbAl(S04)2  +  i2H2O  and  RbFe(SO4)2  +  i2H2O),  and  the 
cobaltic  nitrite  (Rb3Co(NO2)  6,  typical) .  The  salts  of  rubid- 
ium color  the  flame  violet.  The  spectrum  gives  two  lines 
in  the  violet  to  the  right  of  the  caesium  lines  (Rba  and 
Rb£),  also  two  lines  not  so  distinct  in  the  dark  red  (Rby 
and  RbB),  near  the  potassium  red  line,  at  the  left  of  the 
spectrum. 

Estimation,    Separation,    and   Experimental    Work.      Vid. 
Caesium. 


CAESIUM.  9 

CESIUM,  Cs,  132.81. 

Discovery.  Csesium  was  discovered  in  1860  by  Bun- 
sen  and  Kirchhoff  while  they  were  engaged  in  the  spectro- 
scopic  examination  of  a  mother-liquor  from  the  waters  of 
Durkheim  spring  (Pogg.  Annal.  cxui,  337;  Chem.  News  n, 
281).  After  the  removal  of  the  strontium,  calcium,  and 
magnesium,  by  well-known  methods,  and  of  the  lithium 
as  far  as  possible  by  ammonium  carbonate,  the  mother^ 
liquor  was  tested,  and  gave,  in  addition  to  the  potassium, 
sodium,  and  lithium  lines,  two  beautiful  blue  lines  never 
before  observed,  near  the  strontium  blue  lines.  Bunsen 
gave  the  name  Caesium  to  the  newly  discovered  element, 
from  the  Latin  caesius,  the  blue  of  the  clear  sky. 

Occurrence.  Caesium  is  found  in  combination  as 
follows : 

(1)  In  minerals: 

Pollucite,  H2Cs4Al4(SiO3)9,  contains  3i-37%Cs20. 
Lepidolite,  LiK(Al(OH,F)2)-  Al(SiO3)3,  contains  o.  2-0. 7%  Cs2O. 
Beryl,  Be3Al2(SiO3)6,  contains  0-3%  Cs2O. 

(2)  In  certain  mineral  waters,  among  which  are  Durk- 
heim  ( i  liter  contains  about  0.21   mg.  RbCl  and  0.17  mg. 
CsCl),     Nauheim,    Baden-Baden,     Frankenhausen,    Kreuz- 
nacher,  Bourbonne  les  Bains,   Monte  Catino,   Wheal  Clif- 
ford. 

(3)  In  ash  from  some  tobacco. 

Extraction.  Of  the  methods  in  use  for  the  extraction 
of  caesium  the  following  may  serve  as  examples: 

(i)  From  pollucite.  The  finely  powdered  mineral  is  de- 
composed on  a  water-bath  with  strong  hydrochloric  acid, 
and  the  acid  solution  is  treated  in  one  of  three  ways :  (a) 
with  antimony  trichloride,  which  precipitates  the  double 
chloride  of  antimony  and  caesium  (3CsCl-2SbCl3)  (Wells, 
Amer.  Chem.  Jour,  xxvi,  265);  (b)  with  a  solution  of  lead 
chloride  containing  free  chlorine,  which  precipitates  a 
double  chloride  of  caesium  and  tetravalent  lead  (2  CsCl  • 


io  THE  RARER  ELEMENTS. 

PbCU)  (Wells,  Amer.  Jour.  Sci.  [3]  XLVI,  186);  (c)  with  an 
excess  of  ammonium  alum  crystals,  the  liquid  being  then 
allowed  to  crystallize,  and  caesium  alum  coming  down  first 
(CsAl(SO4)2-i2H2O)  (Browning  and  Spencer,  Amer.  Jour. 
Sci.  XLII,  (1916),  279). 

(2)  From  any  silicate.      The   mineral  is   heated  with 
a  mixture  of  calcium  carbonate  and  ammonium  chloride, 
and  the  fused  mass  is  cooled  and  extracted  with  water. 
The  liquid  is  then  evaporated  to  a  small  volume,  and  sul- 
phuric acid  is  added  to  precipitate  the  calcium  as  the  sul- 
phate.    After  filtration,  evaporation  is  continued  until  the 
greater  part  of  the  hydrochloric  acid  has  been  expelled. 
Sodium  or  ammonium  carbonate  is  then  added  to'  complete 
the  removal  of  the  calcium  salt.     Upon  the  addition  of 
chloroplatinic  acid  the  caesium  and  rubidium  are  precipi- 
tated as  the  salts  of  that  acid.     By  the  action  of  hydrogen 
upon  these  salts  the  platinum  is  precipitated,  while  the 
caesium  and  rubidium  chlorides  are  left  in  solution. 

(3)  From  lepidolite.     The  mineral  is   decomposed  by. 
heating  with  a  mixture  of  calcium  fluoride  and  sulphuric 
acid  (via.  Experiment   i). 

The  Element.  A.  Preparation.  Elementary  caesium 
may  be  obtained  (i)  by  heating  caesium  hydroxide  with 
aluminum  to  redness  in  a  nickel  retort  (Beketoff,  Bull. 
Acad.  Petersburg  iv,  247);  (2)  by  heating  caesium  hy- 
droxide with  magnesium  in  a  current  of  hydrogen  (Erd- 
mann  and  Menke,  Jour.  Amer.  Chem.  Soc.  xxi,  259,  420); 
(3)  by  heating  caesium  carbonate  with  magnesium  in  a 
current  of  hydrogen  (Graefe  and  Eckardt,  Zeitsch.  anorg. 
Chem.  xxn,  158);  (4)  by  heating  the  chloride  with  calcium 
(vid.  Lithium). 

B.  Properties.  Caesium,  the  most  positive  of  the  metals, 
is  silvery  white  and  soft.  It  takes  fire  quickly  in  the  air, 
burning  to  the  oxide.  It  melts  at  26°  C.  Like  the  other 
alkaline  metals  it  decomposes  water.  Determinations  of 
its  specific  gravity  range  from  1.88  to  2.4. 


CAESIUM.  U 

Compounds.      A.  Typical  forms.      The    following   are 
typical  compounds  of  caesium : 
Oxides,  Cs2O;  Cs2O2;  Cs2O3;  Cs2O4. 
Hydroxide,  CsOH. 
Carbonates,  Cs2CO3;  CsHC03. 
Chloride,  CsCl. 
Double  chlorides,  AgCl-CsCl;   HgCl2-CsCl;  PbCl4-2CsCl; 

PbCl2-4CsCl;    2BiCl3-3CsCl;    CuCl2-2CsCl;    Cu2Cl2- 

CsCl  ;CdCl2  •  2  CsCl ;  2AsCl3  •  3  CsCl  ;2SbCl3  •  3  CsCl  ;SnCl2  - 

CsCl ;  Fe2Cl6  •  6CsCl ;  CoCl2  •  3  CsCl  ;NiCl2  •  2  CsCl ;  MnCl2  - 

2CsCl;       ZnCl2-3CsCl;      MgCl2-CsCl+6H2O;  AuCl3- 
.  CsCl;  PtCl4.2CsCl;PtCl2-2CsCl;  PdCl2-2CsCl;TeCl4. 

2 CsCl;  TlCl3-3CsCl+H2O;  and  many  others. 
Bromides,  CsBr;  CsBr3;  CsBr5. 

Double bromides,HgBr2  •  CsBr ;PbBr2  •  4CsBr ;  CuBr2  •  2CsBr ; 
CdBr2  -3 CsBr;  2AsBr3  -3CsBr;CoBr2  •  2CsBr;NiBr2  -CsBr; 

ZnBr2  •  2CsBr ;  MgBr2  •  CsBr + 6H2O ;  AuBr3  •  CsBr ;  TeBr4 

•2CsBr;  2TlBr3-3CsBr;  and  many  others. 
Iodides,  Csl;  CsI3;  CsI5. 
Double      iodides,      HgI2-CsI;       PbI2-CsI;       CdI2-3CsI; 

2AsI3  -3CsI ;CoI2  •  2CsI ;ZnI2  ^Csl  ;TeI4 •  2CsI ;  T1I3  •  Csl ; 

and  many  others. 
Mixed   halides,    HgCs3Cl3Br2;      HgCs2Cl2Br2;      HgCsClBr2; 

Hg5CsClBr10;      HgCs3Br3I2;      HgCs2Br2I2;      HgCsBrI3; 

HgCs2Cl2I2;   PbCs4(ClBr)6;   PbCs(ClBr)3;    Pb2Cs(ClBr)5. 
Double  fluorides,  2CsF  •  ZrF4 ;  CsF  •  ZrF4  +  H2O ;  2CsF  •  3ZrF4  + 

2H20. 

lodates,  CsIO3;  2CsIO3-I,O5;  2CsIO3-I2O5+2HI03. 
Nitride,  CsN3  (Jour.  Amer.  Chem.  Soc.  xx,  225). 
Nitrates,  CsNO3;  3CsNO3  -Co(NO3)3  +  H20. 
Sulphates,  Cs2SO4;  CsHSO4;  Cs2S2O7;  Cs2O-8SO3. 
Alums,  CsAl(SO4)2+  i2H2O ;        Cs2SO4-Mn2(SO4)s+  24H2O; 

Cs2SO4  •  Ti2O3  •  380, 
Fluosilicate,  Cs2SiF6. 


I2  THE  RARER  ELEMENTS. 

Chromates,  Cs2UU4,  LsaCr3O7. 

Chloroplatinate,  Cs2PtCl6. 

Cobaltlc  n  trite,  Cs3Co(NO2^6,*  typical. 

B.  Characteristics.  With  few  exceptions  the  caesium 
compounds  are  soluble  in  water.  They  closely  resemble 
the  po  assium  and  rubidium  compounds,  being  for  the 
most  part  isomorphous  with  them.  A  comparison  of  the 
solubilities  of  the  alums  and  also  of  the  chloroplatinates 
of  the  three  elements,  at  a  temperature  of  i5°-i7°C., 
follows : 

100  parts  of  water  will  dissolve 

CsAl(S04)2  -M2H2O,    0.62  parts;   Cs2PtCl6,  0.18  parts. 
RbAl(SO4)2  +  i2H2O,    2.30      "       Rb2PtCl6,  0.20      " 
KA1(S04  2  +i2H20,  13.50     "         K2PtCl6,  2.17     « 

Among  the  important  insoluble  salts  are  the  chloroplatinate 
(Cs2PtCl6),  the  alum  (CsAl(SO4)2  +  i2H2O),  the  cobaltic 
nitrite  (Cs3Co(MO2)6,  typical),  and  the  double  chlorides 
with  tetravalent  lead  (PbCl4- 2CsCl),  tetravalent  tin 
(2CsCl  •  SnCl4 ') ,  and  trivalent  antimony  (3CsCl  •  2SbCl3) .  The 
salts  of  caesium  color  the  flame  violet.  The  spectrum  shows 
two  sharply  denned  lines  in  the  blue,  designated  on  the  scale 
as  Cs^  and  Cs,3. 

Estimation  of  Caesium  and  Rubidium.  Caesium  and  ru- 
bidium may  be  estimated  in  general  by  the  methods  applied 
to  potassium.  They  are  usually  weighed  as  the  normal  sul- 
phates, after  evaporation  of  suitable  salts  with  sulphuric 
acid  and  ^nition  of  the  products;  other  methods,  however, 
such  as  the  chloroplatinate  and  chloride  methods,  are  pos- 
sible. They  may  be  weighed  with  a  fair  degree  of  accuracy 

*  Cs  may  be  partly  replaced  by  Na. 


CAESIUM.  13 

as  the  acid  sulphates,  after  evaporation  with  an  excess  of 
sulphuric  acid,  and  heating  at  25o°-27o°  C.  until  a  constant 
weight  is  obtained  (Browning,  Amer.  Jour.  Sci.  [4]  xn,  301). 
They  may  also  be  estimated  by  precipitation  with  sodium 
cobaltic  nitrite,  decomposition  of  the  cobaltic  nitrites  with 
hydrochloric  acid,  and  precipitation  of  the  perchlorates  by  a 
30%  perchloric  acid  solution*  (Montemartini,  Gaz.  chim. 
ital.  xxxin  (n),  189;  Chem.  Zentr.  1904  (i),  119).  Rubidium 
may  be  estimated  by  means  of  the  spectroscope  by  com- 
paring the  intensity  of  the  spectrum  lines  obtained  from  a 
definite  amount  of  solution  of  rubidium  salt  to  be  estimated 
with  that  of  the  lines  obtained  from  a  definite  amount 
of  a  solution  of  known  strength  (Gooch  and  Phinney, 
Amer.  Jour.  Sci.  [3]  XLIV,  392). 

Separation  of  Caesium  and  Rubidium.  These  metals  belong 
to  the  alkali  group.  From  sodium  and  lithium  they 
may  be  separated  (i)  by  chloroplatinic  acid,  with  which 
they  form  insoluble  salts;  and  (-2)  by  aluminum  sulphate, 
with  which  they  form  difficultly  soluble  alums.  From 
potassium  they  may  be  separated  by  the  greater  solubility 
of  the  potassium  alum  and  chloroplatinate  in  water. 

Cassium  and  rubidium  may  be  separated  from  each 
other  (i)  by  the  difference  in  solubility  of  the  chloroplati- 
nates;*  (2)  by  the  difference  in  solubility  of  the  alums;f 
(3)  by  the  formation  of  the  more  stable  and  less  soluble 
tartrate  of  rubidium;  and  (4)  by  the  solubility  of  caesium 
carbonate  in  absolute  alcohol.  Probably  the  most  satis- 
factory methods,  however,  are  those  suggested  by  Wells; 
they  depend  upon  the  insolubility  of  the  following  salts: 
cassium  double  chloride  and  iodide  (CsCl2I)  (Amer.  Jour. 
Sci.  [3]  XLIII,  17^,  caesium-lead  chloride  (Cs2PbCl6)  (ibid. 
[3]  XLVI,  1 86),  and  cassium-antimony  chloride  (Cs3Sb2Cl9) 
(Amer.  Chem.  Jour,  xxvi,  265). 

*  Vid.  also  Gooch  and  Blake  (Amer.  Jour.  Sci.  [4]  XLIV,  381). 
t  Vid.  p.  12. 


THE  RARER.  ELEMENTS. 


EXPERIMENTAL  WORK   ON    CESIUM  AND 
RUBIDIUM. 

Experiment  i .  Extraction  of  c&sium  and  rubidium  salts 
•from  lepidolite.  Mix  thoroughly  in  a  lead  or  platinum 
dish  100  grm.  of  finely  ground  lepidolite  with  an  equal 
amount  of  powdered  fluorspar.  Add  50  cm.3  of  com- 
inon  sulphuric  acid  and  stir  until  the  mass  has  the 
consistency  of  a  thin  paste.  Set  aside  in  a  draught  hood 
until  the  first  evolution  of  fumes  (SiF4  and  HF)  has  nearly 
•ceased.  Heat  on  a  plate  or  sand-bath  at  a  temperature 
of  2o^°-3oo°  C.  until  ths  mass  is  dry  and  hard.  Pulverize 
and  extract  with  hot  water  until  the  washings  give  no 
precipitate  on  the  addition  of  ammonium  hydroxide  to 
a  few  drops.  Evaporate  the  entire  solution  to  about 
100  cm.3  and  filter  while  hot  to  remove  the  calcium  sul- 
phate. Set  the  clear  filtrate  aside  to  crystallize.*  The 
crystals,  consisting  of  a  mixture  of  potassium,  caesium, 
and  rubidium  alums,  with  some  lithium  salt,  should  be 
dissolved  in  about  100  cm.3  of  distilled  water,  and  allowed 
to  recrystallize.  This  process  of  recrystallization  should 
be  repeated  until  the  crystals  give  no  test  before  the  spec- 
troscope for  either  lithium  or  potassium.  The  amount  of 
caesium  and  rubidium  alums  obtained  will  of  course  vary 
with  the  variety  of  lepidolite  used.  An  average  amount 
of  the  mixed  alums  of  potassium,  caesium,  and  rubidium 
from  the  first  crystallization  would  be  10  grm.  The  pure 
caesium  and  rubidium  alums  finally  obtained  should  be 
about  3  grm.  (Robinson  and  Hutchins,  Amer.  Chem.  Jour, 
vi,  74).  Lithium  may  be  extracted  from  the  mother-liquor 
{md.  Experiment  i,  Lithium). 


*  If  this  solution  is  evaporated  to  a  small  volume  and  saturated  with 
NH4Al(S04)2-i2H2O  the  crystallization  of  the  Cs  and  Rb  alums  will  be  facilitated 
(Browning  and  Spencer). 


EXPERIMENTAL  WORK  ON  CESIUM  AND  RUBIDIUM.          15 

Experiment  2.  Preparation  of  ccesium  and  rubidium 
sulphates  (Cs2SO4;  Rb2SO4).  Dissolve  in  water  a  crystal 
of  the  caesium  and  rubidium  alums  obtained  from  lepido- 
lite,  add  a  few  drops  of  ammonium  hydroxide,  and  boil. 
Filter  off  the  aluminum  hydroxide  and  evaporate  the 
filtrate  to  dryness.  Ignite  until  the  ammonium  sulphate 
is  removed,  dissolve  in  a  few  drops  of  water,  filter,  and 
evaporate  to  dryness.  Sulphates  of  caesium  and  rubidium 
will  remain. 

Experiment  3.  Preparation  of  the  carbonates  of  c&sium 
and  rubidium  (Cs2CO3 ;  Rb2CO3) .  Dissolve  in  water  a  crystal 
of  caesium  and  rubidium  alums  obtained  from  lepidolite, 
add  an  excess  of  barium  carbonate,  and  boil.  Filter  off 
the  alumina,  barium  sulphate,  and  excess  of  barium 
carbonate.  Pass  a  little  carbon  dioxide  through  the  clear 
filtrate  and  boil  to  remove  traces  of  barium  salt.  Filter. 
Carbonates  of  caesium  and  rubidium  will  remain  in  solution. 

Experiment  4.  Formation  of  the  double  chloride  of 
ccssium  and  tetravalent  lead  (2CsCl  -PbClJ.  To  a  few 
cm.3  of  a  one  per  cent,  solution  of  a  caesium  salt  add  a  few 
drops  of  the  reagent  obtained  by  warming  lead  dioxide 
with  hydrochloric  acid  and  allowing  the  solution  to  stand 
until  cool.  Make  a  similar  experiment,  using  a  rubidium 
salt  in  place  of  the  caesium  salt.  Note  the  absence  of  pre- 
cipitation in  this  case. 

Experiment  5.  Precipitation  of  the  double  chloride  of 
cazsium  and  antimony  (3CsCl-2SbCl3).  To  a  few  cm.3  of 
a  one  per  cent,  solution  of  a  caesium  salt  add  some  anti- 
mony trichloride  in  solution  and  evaporate  to  a  small 
volume.  The  double  chloride  will  be  precipitated  on  cool- 
ing. Repeat  the  experiment,  using  a  rubidium  salt.  Note 
the  absence  of  precipitation  in  this  case. 

Experiment  6.  Precipitation  of  the  double  salt  ccesium 
chloride  and  stannic  chloride  (2CsCl-SnCl4).  Make  an  ex- 


1 6  THE  RARER  ELEMENTS. 

criment  similar  to  Experiment  5,  using  stannic  chloride 
in  the  place  cf  antimonious  chloride.  Note  the  separa- 
tion'of  the  double  chloride  on  cooling.  Make  a  similar 
experiment,  using  a  rubidium  salt. 

Experiment  7.  Precipitation  of  the  chloroplatinates  of 
casium  and  rubidium  (Cs2PtCl6;  Rb2PtCl6).  To  a  few 
cm.3  of  a  solution  of  a  caesium  salt  add  a  few  drops  of  a 
solution  of  chloroplatinic  acid.  Make  a  similar  experiment 
with  a  solution  of  a  rubidium  salt. 

Experiment  8.  Precipitation  of  the  cobaltic  nitrites  of 
caesium  and  rubidium.  Try  the  action  of  a  solution  of  sodi- 
um cobaltic  nitrite  upon  separate  solutions  of  caesium  and 
rubidium  salts. 

Experiment  9.  Precipitation  of  the  alums  of  ccesium  and 
rubidium.  To  a  few  drops  of  a  concentrated  solution  of 
a  caesium  salt  add  about  5  cm.3  of  a  saturated  solution  of 
ammonium  alum.  Note  the  precipitation  of  the  caesium 
alum.  Make  a  similar  experiment  with  a  rubidium  salt. 

Experiment  10.  Flame  tests  for  c&sium  and  rubidium. 
Dip  the  end  of  a  platinum  wire  into  a  solution  of  a  caesium 
salt  and  test  the  action  of  the  flame  of  a  Bunsen  burner 
upon  it.  Repeat,  using  a  rubidium  salt. 

Experiment  n.  Spectroscopic  tests  for  c&sium  and 
rubidium.  Test  solutions  of  caesium  and  rubidium  salts 
before  the  spectroscope.  Note  the  twin  blue  lines  of  the 
caesium  spectrum  and  the  twin  violet  lines  of  the  rubidium. 

Experiment  12.  Negative  tests  of  c&sium  and  rubidium. 
Note  that  hydrogen  sulphide,  ammonium  sulphide,  and 
ammonium  carbonate  give  no  precipitates  with  salts  of 
caesium  and  rubidium. 


CHAPTER  II. 

BERYLLIUM,  Be,  9.1. 

Discovery.  In  the  year  1 797,  Vauquelin  discovered  beryl- 
lium or  glucinum  in  the  mineral  beryl  (Ann.  de  Chim.  xxvi, 
155).  After  having  removed  the  silica  in  the  usual  manner, 
he  precipitated  with  carbonate  of  potassium,  and  treated  the 
precipitate  with  a  solution  of  caustic  potash.  The  greater 
part  of  the  precipitate  dissolved,  but  the  presence  of  some- 
thing other  than  alumina  was  shown  by  precipitation 
when  the  solution  was  boiled.  The  new  precipitate,  dis- 
solved in  sulphuric  acid,  gave  on  evaporation  irregular 
crystals  having  a  sweetish  taste  and  forming  no  alum  with 
potassium  sulphate.  In  his  early  articles  Vauquelin  refers 
to  the  oxide  as  "  la  terre  du  Beril,"  which  the  German  chem- 
ists translated,  "  Berylerde."  The  sweet  taste  suggested 
for  the  new  element  the  name  Glucinum,  from  yAv/cvs, 
sweet.  The  name  Beryllium,  from  the  chief  source,  beryl, 
has  been  more  generally  used. 

Occurrence.     Beryllium  occurs  in  minerals  as  follows : 
Beryl,  Be3Al2(SiO3)6,          contains  u-i5%BeO. 

Chrysoberyl,  BeAl2O4,  "         19-20%    " 

Bertrandite,  Be2(Be-OH)2Si2O7,      "         40-43%    " 

Phenacite,  Be2SiO4,  "         44-46%    " 

Leucophanite,  Na(BeF)Ca(SiO3)2,      "         10-12%    " 

Meliphanite,  NaCa2Be2FSi3O10         "         10-14%    " 

Epididymite,  HNaBeSi3O8,  "         10-11%    " 

Euclase,  Be(Al-OH)SiO4,          "         17-18%    " 

Helwte  or  danalite,   R6(R2S)(SiO4)3,  "        13-14%     " 

17 


THE  RARER  ELEMENTS. 


Gadotinite, 

Trimerite, 

Cyrtolite, 

Alvite, 

Allanite, 

Muromonite, 

Erdmanite, 

Foresite, 

Arrhenite, 

Beryllionite, 

Herderite, 

Hambergite, 

Sipylite, 

Tengerite, 


FeBe2Y2Si2Oio, 
Be(Mn,Ca,Fe)Si04, 
complex  silicate, 


contains    5-11%  BeOv 
16-17%    " 
14-15%    ' 
circa  14% 


complex  silico-tantalate, 
NaBePO4, 
Ca(Be(OH,F))P04) 
Be(BeOH)B03, 

ErNb04. 

complex  carbonate, 


5-6% 

o-4% 

0-1% 

circa  i%    " 

19-20%     " 

15-16%    " 

53-54%     " 
circa  .6%    " 


Beryllium  is  found  also  in  traces  in  some  monazite 
sands  and  aluminous  schists,  and  in  some  mineral  waters. 

Extraction.  Ben-Ilium  is  generally  extracted  from  beryl 
by  one  of  the  following  methods  : 

(1)  The    mineral   is  fused  with   sodium   or  potassium 
hydroxide  (vid.  Experiment  i). 

(2)  The  finely  ground  mineral  is  fused  with  three  times 
its  weight  of  potassium  fluoride.    The  fused  mass  is  treated 
with  strong  sulphuric  acid  and  warmed;  by  this  process 
the  silica  is  removed  as  silicon  fluoride,  and  the  alumina 
and  potash  are  united  to  form   the  alum,  which  may  be 
crystallized  out  on  evaporation.     The   beryllium  remains 
in  solution  as  the  sulphate,  and  may  be  removed  by  the 
treatment  described  in  Experiment  i. 

(3)  The  mineral   is  fused  with  calcium  fluoride.     This 
process  is  in  general  the  same  as  the  one  indicated  in  the 
second  method,  except    that  calcium  sulphate  is  formed 
and  must  be  removed   (Lebeau,  Chem.  News  LXXIII,  3). 

(4)  The  mineral  is    decomposed    by  fusion    (a)    with 


BERYLLIUM.  19 

sodium  and  potassium  carbonates,  or  (6)  with  acid 
potassium  sulphate. 

The  Element.*  A.  Preparation.  Elementary  beryllium 
may  be  obtained  (i)  by  bringing  together  the  vapor  of 
the  chloride  and  sodium  in  a  current  of  hydrogen  (De- 
bray,  Ann.  Chim.  Phys.  (1855)  XLIV,  5);  (2)  by  fusing  the 
chloride  with  potassium  (Wohler,  Pogg.  Annal.  xm,  577); 
(3)  by  heating  the  chloride  in  a  closed  iron  crucible  with 
sodium  (Nilson  and  Pettersson,  Ber.  Dtsch.  chem.  Ges.  xi, 
381 , 906) ;  (4)  by  electrolyzing  the  double  fluoride  of  beryllium 
and  sodium  or  potassium  (Lebeau) ;  (5)  by  heating  the 
chloride  in  a  bomb  with  sodium  (Hunter). 

B.  Properties.  The  element  beryllium  is  dark  steel-gray 
in  color.  At  ordinary  temperatures  unchanged  in  air  and 
in  oxygen,  it  burns  brightly  to  the  oxide  when  heated  in 
either.  It  does  not  decompose  hot  or  cold  water.  When 
heated  it  combines  readily  with  fluorine,  chlorine,  bromine 
and  iodine.  It  is  soluble  in  dilute  and  in  concentrated  acids; 
also  in  potassium  hydroxide  with  the  liberation  of  hydrogen. 
Determinations  of  its  specific  gravity  range  from  1.75  to 

1.85- 

Alloys  of  beryllium  with  many  of  the  common  metals 
are  known,  as  are  also  alloys  with  chromium,  molybdenum 
and  tungsten  (Lebeau) .  An  alloy  of  copper  and  beryllium 
containing  from  .5%  to  1.3%  beryllium  is  very  sonorous. 

Compounds.  A.  Typical  forms.  The  following  are 
typical  compounds  of  beryllium: 

Fluorides,  BeF2;  BeF2.2NaF;  BeF2.2KF;  BeF2.2NH4F. 
Chlorides,    BeCl2;    BeCl2.AuCl3;    BeCl2.FeCl3.H20;    BeCl2. 

CrCl3.H20;    3BeCl2.Tl2Cl6;     BeCl2.2lCl3.8H2O;    BeCl2. 

PtCl2.5H20;       BeCl2.PtCl4.8H20;      BeCl2.PdCl2.6H20; 

BeCl2.PdCl4.8H20. 
Bromide,  BeBr2. 
Iodide,  BeI2. 

*  Vid.  also  Fichter  and  Jablczynski,  Ber.  dtsch.  chem.  Ges.  XLVI,  1604. 


20  THE  RARER  ELEMENTS. 

Hydroxide,  Be(OH)3  . 

Oxide,  BeO. 

Sulphide,  BeS. 

Cyanides,  BePt(CN)4.4H20;     BeMg2Pt3(CN)i2;      BePtBr2 

(CN)4. 

Carbides,  Be2C;  3Be2C.B6C. 
Nitride,  Be3N2. 
Sulphates,    BeS04;     BeSO4.2H20;     BeS04.4H20;    BeS04. 

K2S04.2H20;      BeS04.K2S04.KHS04.4H20;      3BeS04. 

2Na2SO4.i2H2O;  BeS04.(NH4)2S04.2H2O. 
Sulphites,  BeSO3.H20;  BeSO3.2H20;  2BeS03.K2S03.9H20; 

2BeS03.(NH4)2S03.4H20. 
Selenate,  BeSeO4.4H20. 
Selenites,  BeSeO3.H20;  BeSc03.2H20. 
Nitrate,  Be(N03)2.4H20. 
Phosphates,  BeHP04-3H20;    BeKP04;    BeNaP04;   BeNaj 

(NH4)2(P04)2. 

Antimonate,  Be(SbO3)2.6H20. 
Carbonate,  *BeC03/yBe(OH)2. 
Silicates,  BeSiO3;  Be3Al2(Si03)6. 
Aluminate,  Be(A102)2. 
Methyl,  Be(CH3)2. 
Ethyl,  Be(C2H5)2. 
Fropyl,  Be(C3H7)2. 

Acetates,  Be(C2H3O2)2;  Be40(C2H302)6. 
Acetylacetonaie,  Be(C5H7O2)2. 
Oxalates,  BeC2O4.3H2O;  BeC2O4.K2C204;  etc. 
Tartrates,  BeC4H4O6.3H20;     KBeC4H306;    K2Be4C8H4Oi3. 

7H20;  Na2Be4C8H4Oi3.ioH20. 

and  many  salts  of  organic  acids;  e.  g.,  succinates,  racemates, 
malates,  formates,  propionates,  butyrates,  trichloracetate 
(Parsons  and  Sargent,  Jour.  Amer.  Chem.  Soc.  xxxi, 
1202). 

B.  Characteristics.  The  compounds  of  beryllium  closely 
resemble  those  of  aluminum.  The  oxide  is  white;  it  is 
insoluble  in  water  and  unaffected  by  it.  The  hydroxide  i0 


BERYLLIUM.  21 

soluble  in  concentrated  solutions  of  its  own  salts  and  is 
precipitated  from  them  by  dilution.  It  is  also  soluble  in 
the  alkali  hydroxides  and  bicarbonates,  and  in  dilute  acids. 
The  halides  are  very  readily  hydrolyzed  by  water,  the  hy- 
drolysis in  the  case  of  the  chlorides,  bromides,  and  iodides 
being  practically  complete.  Normal  salts  of  the  non- volatile 
acids  only  can  be  crystallized  from  water;  of  these  the 
sulphate,  oxalate,  and  selenate  are  examples.  The  nitrate 
can  be  prepared  only  by  crystallization  from  strong  nitric  acid. 

The  double  alkali  tartrates  are  of  peculiar  interest,  both 
on  account  of  the  fact  that  beryllium  appears  to  replace 
not  only  the  positive  hydrogen  of  the  acid  but  also  in  part 
the  hydrogen  of  the  tartrate  ion,  and  also  because  the  pres- 
ence of  beryllium  in  the  salt  increases  the  molecular  rotation. 
This  influence  upon  the  molecular  rotation  is  shown  to  an 
even  greater  degree  in  the  case  of  the  malates  (Rosenheim 
and  Itsig).  Another  interesting  compound  is  the  basic 
acetate,  which,  although  almost  insoluble  in  water,  becomes 
soluble  after  hydrolysis  by  hot  or  cold  water.  It  is  soluble 
without  decomposition  in  glacial  acetic  acid,  methyl,  ethyl, 
and  amyl  alcohols,  chloroform,  turpentine, ether  acetone, car- 
bon disulphide,  and  some  other  organic  solvents.  It  is  un- 
affected by  dry  air,  melts  at  283°-284°  C.,  boils  at  33o°-33i° 
C.,  and  may  be  sublimed.  It  was  used  by  Parsons  in  deter- 
mining the  atomic  weight  of  beryllium.  It  is  best  prepared 
by  the  action  of  glacial  acetic  acid  upon  the  dry  carbonate 
or  hydroxide.  The  chloride,  nitrate  and  sulphate  are  the 
common  soluble  salts,  and  the  nitrate  and  chloride  are 
soluble  in  alcohol. 

The  arc  spectrum  of  beryllium  is  characterized  by  lines 
in  the  blue  and  indigo. 

Estimation.  Beryllium  is  ordinarily  estimated  as  the 
oxide,  (BeO),  which  is  obtained  by  the  ignition  of  the 
precipitated  hydroxide. 

Separation.  Beryllium  closely  resembles  aluminum  in 
many  reactions.  It  may  be  separated  from  aluminum  (i) 


22  THE  RARER  ELEMENTS. 

by  the  action  of  a  saturated  solution  of  acid  sodium  carbonate 
upon  the  hydroxides  of  iron,  aluminum  and  beryllium,  beryl- 
lium hydroxide  being  dissolved  (Parsons  and  Barnes) ;  (2) 
by  saturation  of  a  solution  of  the  two  chlorides  with  hydro- 
chloric acid  gas  in  the  presence  of  ether,  the  beryllium  re- 
maining in  solution,  while  the  aluminum  chloride  is  precipi- 
tated (Gooch  and  Havens,  Amer.  Jour.  Sci.  [4]  n,  416); 
(3)  by  the  action  of  hot  glacial  acetic  acid  upon  the  acetates, 
basic  beryllium  acetate  separating  out  on  cooling  (Parsons 
and  Robinson);  (4)  by  dehydration  of  the  nitrates  with 
amyl  alcohol,  the  beryllium  nitrate  dissolving  (Browning 
and  Kuzirian) ;  (5)  by  heating  the  acetates,  the  beryllium 
acetate  subliming  (Kling  and  Gelin,  Bull.  Soc.  Chim.  [4] 
xv,  205 ;)  (6)  by  the  action  of  acetyl  chloride  in  acetone  on 
the  chlorides  (Minnig,  Amer.  Jour.  Sci.  XL,  482). 


EXPERIMENTAL  WORK  ON  BERYLLIUM. 

Experiment  i.  Extraction  of  beryllium  salts  from  beryl 
(BesA^SieOis).  Fuse  in  a  nickel  or  iron  crucible  10  grm.  of 
finely  powdered  mineral  with  10  grm.  of  potassium  hydrox- 
ide, and  cool.  Pulverize  the  fused  mass,  add  water  enough  to 
cover  it,  and  strong  sulphuric  acid  in  slight  excess.  Heat 
the  gelatinous  mass  until  fumes  of  sulphuric  acid  are  given 
off  and  the  residue  has  the  appearance  of  a  fine  white 
powder.  Extract  thoroughly  with  hot  water,  discarding  the 
insoluble  material.  Evaporate  until  the  alums  begin  to 
crystallize  from  the  solution,  and  allow  to  stand,  when  the 
greater  part  of  the  aluminum  will  separate  as  the  alum. 
Treat  the  mother  liquor  from  the  alum  with  nitric  acid,  to 
convert  all  iron  present  to  the  ferric  condition,  neutralize 
with  ammonium  hydroxide,  and  add  sodium  acid  carbonate 
in  crystals  to  saturation,  warming  gently  (50°  C.),  with  fre- 
quent stirring  for  about  an  hour;  or,  if  the  quantity  of  hy- 
droxide is  small,  bring  rapidly  to  boiling  and  boil  for  one 
minute  only.  Filter,  add  a  little  ammonium  sulphide  to 


EXPERIMENTAL    WORK  ON  BERYLLIUM.  23 

remove  any  iron  in  solution,  filter,  and  dilute  with  about 
five  or  ten  volumes  of  water.  Pass  steam  through  the. 
liquid,  or  boil  if  the  amount  of  beryllium  is  small,  to  pre- 
cipitate the  basic  carbonate  of  beryllium  (Parsons). 

Experiment  2.  Precipitation  of  beryllium  hydroxide- 
(Be(OH)2).  (a)  To  a  solution  of  a  beryllium  salt  add  am- 
monium hydroxide,  and  note  the  insolubility  of  the  precipi- 
tate in  excess  of  that  reagent. 

(6)  To  another  portion  of  the  beryllium  solution  add 
a  solution  of  potassium  or  sodium  hydroxide,  and  note 
the  solvent  action  of  an  excess. 

(c)  Dilute  with  water  a  portion  of  the  alkaline  solution 
obtained  in  (6)  and  boil.     Note  the  reprecipitation  of  the 
hydroxide. 

(d)  To  another  portion  of  the  alkaline  solution  obtained 
in  (6)  add  ammonium  chloride,  and  boil. 

(<?)  To  a  solution  of  a  beryllium  salt  add  ammonium 
sulphide. 

Experiment  3.  Precipitation- of  basic  beryllium  carbonate 
(^BeC03jBe(OH)2).  (a)  To  a  solution  of  a  beryllium  salt 
add  sodium  or  potassium  carbonate  in  solution.  Note  the 
solvent  action  of  an  excess  and  the  reprecipitation  on  boil- 
ing. 

(6)  Make  a  similar  experiment,  using  ammonium  car- 
bonate. Note  solubility  in  excess. 

Experiment  4.  Precipitation  of  beryllium  phosphate 
(Be3(PO4)2).  To  a  solution  of  a  beryllium  salt  add  a  solution 
of  sodium  phosphate. 

Experiment    5.     Preparation   of   beryllium    basic   acetate 
(Be-iCXCoHsC^e).     Dissolve  some  beryllium  hydroxide  or 
carbonate  in  acetic  acid  and  evaporate  to  dryness.     Dis- 
solve the  dry  residue  in  excess  of  hot  glacial  acetic  acid  and  j 
allow  the  solution  to  cool. 

Experiment  6.  Action  of  sodium  acid  carbonate  and  of 
ammonium  carbonate  upon  beryllium  hydroxide,  (a)  To  a 
small  amount  of  washed  beryllium  hydroxide  add  2-3  grrcu 


24  THE  RARER  ELEMENTS. 

of  solid  sodium  acid  carbonate  and  20  cm.3  of  water,  and 
heat  rapidly  to  boiling.  Note  the  solubility  of  the  hydroxide. 
Dilute  to  200  cm.3  and  boil.  Note  the  precipitation  of  the 
hydroxide. 

(6)  Try  similarly  the  action  of  ammonium  carbonate, 
and  note  the  solubility  of  the  hydroxide  in  that  reagent. 

Experiment  7.  Solubility  of  beryllium  salts  in  amyl 
alcohol.  To  a  few  drops  of  a  solution  of  beryllium  chloride 
or  nitrate  add  5  cm.3  of  amyl  alcohol  and  bring  to  the  boiling 
point  of  the  alcohol.  Note  the  solubility  of  the  salts  in 
the  alcohol. 

Experiment  8.  Negative  tests  of  beryllium  salts.  Try 
the  action  of  hydrogen  sulphide  and  ammonium  oxalate 
upon  separate  portions  of  a  solution  of  a  beryllium  salt. 
Add  sodium  acetate  to  a  solution  of  a  beryllium  salt  and 
boil.  Note  the  absence  of  precipitation  in  each  case. 


CHAPTER   IIL 
THE   RADIO-ELEMENTS.* 

THE  property  of  matter  known  as  radioactivity  was  di& 
covered  in  1896  by  M.  Henri  Becquerel,  who  observed  that 
the  salts  of  uranium  emitted  a  characteristic  radiation 
which  was  capable  of  producing  an  effect  on  a  photographic 
plate  through  several  thicknesses  of  black  paper  wholly 
opaque  to  ordinary  light. 

The  radiation  emitted  by  radioactive  substances  has 
been  shown  to  be  complex  in  character  and  to  include  three 
distinctive  types  known  as  the  a,  3  and  /-  radiations. 

The  a  radiation  consists  of  positively  electrified  atoms 
of  helium  moving  with  a  velocity  equal  to  about  1-15 
of  the  velocity  of  light.  The  a  rays  are  completely  stopped 
by  thin  layers  of  ordinary  matter  and  are  deflected  by 
strong  magnetic  and  electrostatic  fields. 

The  $  radiation  consists  of  negatively  electrified  par- 
ticles having  a  mass  about  one  eighteen-hundredth  that 
of  a  hydrogen  atom  and  projected  at  a  velocity  which 
in  some  cases  is  as  high  as  nine-tenths  the  velocity  of 
light.  The  £  rays  have  a  greater  power  for  penetrating 
matter  than  the  a  rays,  but  are  more  readily  deflected 
than  the  latter  by  both  magnetic  and  electrostatic  fields. 

The  v  radiation  is  believed  to  consist  of  ether  pulses 
travelling  with  the  velocity  of  light,  and  analogous  in  many 

*  This  chapter  was  contributed  by  Bertram  B.  Boltwood,  Ph.D.,  of  Yale  Uni- 
versity. 

25 


26  THE  RARER  ELEMENTS, 

respects  to  the  Roentgen  or  X  radiation.  The  ?  rays  have 
a  high  penetrative  power  and  are  not  affected  by  either 
electrostatic  or  magnetic  fields. 

All  three  types  of  radiation  are  capable  of  producing 
charged  carriers  of  electricity,  known  as  ions,  in  the  gases 
which  they  traverse,  and  in  this  manner  render  the  gases 
conductive  to  electricity.  They  also  excite  phosphores- 
cence in  various  chemical  compounds  and  produce  an  effect 
on  photographic  plates. 

The  chemical  elements  which  exhibit  the  phenomena  of 
radioactivity  are  termed  radio-elements.  In  order  to 
explain  their  behavior,  a  theory,  known  as  the  disintegration 
theory,  was  proposed  in  1902  by  Rutherford  and  Soddy 
and  has  now  been  generally  accepted.  In  this  theory  it 
is  assumed  that  the  radio-elements  represent  unstable  forms 
of  matter  the  atoms  of  which  are  spontaneously  undergoing 
changes  which  result  in  the  production  of  new  forms  of 
matter  having  different  physical  and  chemical  properties. 
These  changes  are  accompanied  by  the  emission  of  energy 
usually  appearing  in  the  form  of  heat  derived  from  the 
internal  energy  of  the  atoms  in  process  of  transformation. 
The  disintegration  of  the  radio-elements  takes  place  accord- 
ing to  a  simple  exponential  law  which  is  given  by  the 
expression  N=N0£~X/,  where  N0  is  the  number  of  ctoms 
of  the  element  present  at  the  start,  N  is  the  number  remaining 
unchanged  after  any  time  t,  e  is  the  base  of  the  natural 
system  of  logarithms  and  \  is  the  constant  of  change  of 
the  given  element.  The  constant  of  change  is  a  definite 
and  characteristic  quantity  for  any  particular  radio-element 
•and  its  value  is  unaffected  by  any  of  the  extremes  of  tem- 
perature and  pressure  to  which  it  has  been  possible  to  subject 
radioactive  substances.  The  constant  of  change  represents 
the  fraction  of  any  given  quantity  of  the  radio-element 
which  undergoes  transformation  in  the  unit  of  time. 

The  disintegration  of  the  radio-elements  is  wholly  inde- 


THE  RADIO-ELEMENTS.  27 

pendent  of  the  chemical  state  or  form  of  combination  of  the 
radio-elements,  and  proceeds  at  a  constant  rate  which  is  the 
same  in  all  compounds  of  the  same  element.  As  a  necessary 
consequence  of  this  fact  the  relative  radioactivity  of  different 
chemical  compounds  of  the  same  radio-element  is  directly 
proportional  to  the  relative  quantities  of  the  element  which 
they  each  contain. 

The  instability  of  atomic  structure  may  continue  through 
a  considerable  number  of  successive  changes  until  a  final 
stable  form  of  matter  is  reached.  A  radio-element  from 
which  any  other  radio-element  is  formed  is  called  the  ".par- 
ent" of  the  latter  and  the  element  formed  is  known  as 
the  "product"  of  the  parent  from  which  it  is  produced. 

The  known  radio-elements  can  be  divided  into  two 
general  groups:  the  uranium  series  and  the  thorium  series. 
The  uranium  series  comprises  uranium  and  twTenty-three 
products  of  uranium,  including  ionium,  radium,  actinium, 
and  polonium.  The  thorium  series  contains  ten  members 
in  addition  to  thorium  itself.  The  chemical  behavior  of 
the  radio-elements,  with  the  exception  of  uranium,  radium, 
ionium,  mesothorium,  and  thorium,  has  not  been  completely 
investigated,  but  there  is  every  reason  for  believing  that 
they  all  possess  distinct  and  characteristic  chemical  prop- 
erties. 

THE  RADIO-ELEMENTS  AND  THE  PERIODIC 
TABLE. 

The  study  of  radioactivity  has  led  to  the  discovery  and 
identification  of  no  less  than  thirty-three  new  and  hitherto 
unsuspected  elementary  forms  of  matter  or  radio-elements. 
When  the  existence  of  the  greater  number  of  these  had  been 
recognized  it  appeared  at  first  sight  to  be  quite  impossible 
to  find  any  places  for  them  in  the  Periodic  Table.  A  po- 
sition could  be  found  for  radium  in  Group  II  in  the  ninth 
horizontal  row  under  barium,  which  corresponded  satis- 


28  THE  RARER  ELEMENTS. 

factorily  to  its  atomic  weight  and  chemical  properties,  but 
there  appeared  to  be  an  insufficient  number  of  vacant  spaces 
to  accommodate  the  greater  number  of  other  radio-elements. 
This  obstacle  was  overcome  by  the  recognition  of  the  fact 
that  the  position  of  the  various  elements  in  the  Periodic 
Table  was  determined  by  the  value  known  as  the  atomic 
number  of  each  element  rather  than  by  its  atomic  weight 
as  had  previously  been  assumed.  The  atomic  number  of 
an  element  is  dependent  on  the  electrical  structure  of  the 
atom  and  can  be  determined  directly  by  suitable  experi- 
mental methods.  Since  the  position  of  an  element  in  the 
Periodic  Table  is  established  by  its  atomic  number,  and 
since  the  value  of  the  atomic  number  is  not  directly  depend- 
ent on  the  atomic  weight,  it  is  apparently  possible  for  two 
elements  to  have  different  atomic  weights  and  yet  have 
identical  atomic  numbers,  and  therefore  to  occupy  the  same 
space  in  the  Periodic  Table.  Further,  since  the  chemical 
properties  and  probably  also  the  spectra  of  the  elements 
are  dependent  on  the  atomic  numbers,  it  is  possible  for  two 
different  elements  to  have  identical  chemical  properties  and 
to  show  an  identical  spectrum.  Such  elements  can  be 
separately  identified  only  by  their  different  atomic  weights 
or  by  means  of  some  property  which  is  independent  of 
their  chemical  characteristics.  The  radioactive  properties 
of  the  radio-elements  offer  such  an  independent  means  of 
identification.  Radio-elements  have  been  found  which  are 
absolutely .  inseparable  chemically  from  other  well-known 
inactive  elements  and  many  cases  are  recognized  of  radio- 
elements  which  are  inseparable  from  other  radio-elements. 
Elements  which  show  this  identity  with  other  elements  are 
called  isotopes  and  their  properties  are  said  to  be  isotopic. 

Through  the  application  of  the  theory  of  isotopes  and 
the  calculation  or  determination  of  the  atomic  numbers  of 
the  radio-elements  it  has  been  possible  to  assign  suitable 
positions  to  them  in  the  last  two  rows  of  the  Periodic  Table. 
As  a  matter  of  fact  the  existence  of  the  radio-elements  has 


THE  RADIO-ELEMENTS.  29 

led  to  an  extension  of  our  knowledge  and  a  better  under- 
standing of  the  significance  of  the  periodic  sequence  of  the 
elements. 

URANIUM,  U,  238.5. 

The  general  properties  of  uranium  will  be  discussed  in 
Chapter  VIII.  It  is  one  of  the  most  slowly  changing  of  the 
radio-elements,  its  rate  of  disintegration  corresponding  to 
the  transformation  in  one  year  of  about  one  eight-billionth  of 
the  total  amount  of  uranium  present.  The  time  required 
for  exactly  one-half  of  any  given  quantity  of  uranium  to  dis- 
integrate completely  into  other  forms  of  matter  is  about  five 
billion  years.  Ordinary  uranium  is  supposed  to  consist  of  a 
mixture  of  two  isotopic  elements,  uranium  i  with  an  atomic 
weight  of  238  and  uranium  2  with  an  atomic  weight  of  234. 
Uranium  when  completely  freed  from  its  disintegration 
products  emits  only  a  rays,  but  unless  freshly  prepared  its 
compounds  contain  uranium  X,  which  is  the  source  of  both 
a  /3  and  a  f  radiation.  Uranium  salts  can  be  obtained  free 
from  uranium  X  by  recrystallization,  the  uranium  X  re- 
maining in  the  mother  liquor. 

Uranium  X.  Uranium  X  is  the  first  disintegration  prod- 
uct of  uranium  and  is  gradually  formed  in  uranium  salts 
on  standing.  The  amount  which  accumulates  reaches  a 
maximum  after  about  150  days,  when  a  state  of  radioactive 
equilibrium  is  reached  and  the  amount  of  uranium  X  which 
is  produced  in  any  subsequent  time  is  exactly  equal  to  the 
amount  which  disintegrates  in  the  same  period.  Uranium 
X  was  first  discovered  by  Crookes  in  1900.  It  emits  /3  and 
f  rays,  and  in  24  days  one-half  of  any  given  quantity  of  it 
is  transformed  into  other  substances.  It  can  be  obtained 
free  from  uranium  by  treating  pure  uranium  nitrate,  dried 
at  118°,  with  ordinary  ether.  The  uranium  nitrate  is  dis- 
solved by  the  ether,  leaving  a  slight  residue  which  contains 
the  greater  part  of  the  uranium  X.  Uranium  X  is  isotopic 
with  thorium  and  when  freshly  prepared  consists  of  a  mix- 


30  THE  RARER  ELEMENTS. 

ture  of  two  isotopic  elements,  uranium  Xi,  and  uranium 
X2. 

IONIUM,  lo. 

Ionium  is  a  radio-element  intermediate  between  ura- 
nium, of  which  it  is  a  product,  and  radium,  of  which  it  is  the 
parent.  It  was  discovered  by  Boltwood  in  1907.  It  has 
not  been  obtained  pure  in  sufficient  quantity  to  permit  a 
determination  of  its  atomic  weight  or  of  its  spectrum,  but 
atomic  weight  determinations  on  mixtures  of  ionium  with 
thorium  give  good  agreement  with  the  theoretical  assump- 
tion that  its  atomic  weight  is  about  230.  From  uranium 
minerals  containing  thorium  the  ionium  is  separated  with 
the  thorium,  with  which  it  is  isotopic.  The  constant  of 
change  of  ionium  has  riot  yet  been  determined,  but  its  rate 
of  transformation  is  very  possibly  as  slow  as  that  of  radium. 


RADIUM,  Ra,  226.5. 

Discovery.  Radium  was  discovered  in  1898  by  P.  and 
S.  Curie  and  G.  Bemont.  In  the  course  of  an  investigation 
of  the  relative  radioactivity  of  certain  uranium  salts  and 
uranium  minerals  it  was  noted  by  Mme.  Curie  that  although 
the  activity  of  the  uranium  salts  was  quite  closely  pro- 
portional to  the  amounts  of  uranium  contained  in  them,  the 
activity  of  the  uranium  minerals  was  much  greater  than  was 
to  be  expected  from  the  uranium  which  they  contained. 
This  suggested  that  there  might  be  present  in  the  minerals 
some  other  more  strongly  radioactive  constituent,  and  a 
further  investigation  led  to  the  isolation  of  a  highly  radio- 
active substance  resembling  barium  in  its  chemical  proper- 
ties. 

Occurrence.  Radium  has  been  found  widely  distributed 
in  minute  proportions  in  many  rocks  and  minerals,  in  sea 
water  and  in  the  waters  of  certain  mineral  springs.  The 


THE  RADIO-ELEMENTS.  31 

chief  source  of  radium  has  been  the  minerals  containing  a 
higher  proportion  of  uranium,  principally  carnotite,  and 
the  present  supply  has  been  largely  obtained  from  the 
carnotite  ores  of  southwestern  Colorado.  One  of  the  early 
sources  of  supply  was  the  insoluble  residues  remaining  after 
the  treatment  of  pitchblende  for  the  commercial  extraction 
of  uranium. 

Extraction.  From  pitchblende  residues.  These  consist 
chiefly  of  the  sulphates  of  lead  and  calcium,  together  with 
the  oxides  of  silicon,  aluminum  and  iron.  They  also  contain 
greater  or  less  quantities  of  nearly  all  the  metals  (copper, 
bismuth,  zinc,  cobalt,  manganese,  nickel,  vanadium,  anti- 
mony, thallium,  the  rare  earths,  niobium,  tantalum,  arsenic, 
barium,  etc.).  They  are  first  treated  with  boiling,  concen- 
trated sodium  hydroxide  solution,  washed  with  water,  and 
digested  with  hydrochloric  acid.  Much  of  the  material  is 
removed  in  this  operation,  the  radium  remaining  in  the  un- 
dissolved  portion.  After  further  washing,  the  residue  is 
boiled  with  a  concentrated  sodium  carbonate  solution  which 
converts  the  alkali-earths  into  carbonates.  The  residue  is 
again  washed  to  remove  all  traces  of  sulphates,  and  is  then 
treated  with  hydrochloric  acid,  which  dissolves  the  barium 
and  radium  together  with  certain  of  the  other  constituents. 
The  solution  of  the  chlorides  is  further  purified  until  a  salt 
containing  only  barium  and  radium  is  obtained.  The  mixed 
chlorides  of  barium  and  radium  are  subjected  to  a  long 
series  of  fractional  recrystallizations,  the  radium  being  con- 
centrated in  the  least  soluble  portion  of  the  fractions.  In 
this  manner  a  pure  chloride  of  radium  is  ultimately  obtained. 
The  concentration  of  the  radium  proceeds  more  rapidly  if 
the  recrystallization  is  conducted  with  the  double  bromide. 

From  carnotite.  The  ore  is  decomposed  by  nitric  acid, 
and  barium  chloride  is  added  to  the  solution  in  the  pro- 
portion of  two  pounds  of  barium  chloride  to  one  ton  of  ore. 
The  radium  barium  sulphate  is  then  precipitated  by  sul- 
phuric acid  and  the  sulphate  is  reduced  with  carbon  to  the 


32  THE  RARER  ELEMENTS. 

sulphide.  The  sulphide  is  dissolved  in  hydrochloric  acid 
and  the  radium  barium  chloride  is  subjected  to  fractional 
crystallization  (Parsons,  Moore,  Lind  and  Schaefer, 
Bureau  of  Mines,  Bull.  104,  page  30  (1915)). 

The  Element.  By  the  electrolysis  of  a  solution  of 
radium  chloride  with  a  mercury  cathode,  S.  Curie  and 
Debierne  in  1910  obtained  radium  amalgam  which  on 
distillation  in  hydrogen  left  a  residue  of  metallic  radium. 
It  is  a  white  metal  melting  at  about  700°.  It  alters  rapidly 
in  the  air  with  the  formation  of  nitride  and  decomposes 
water  with  the  formation  of  the  hydroxide. 

Compounds.  A.  Typical  forms.  The  following  com- 
pounds of  radium  have  been  described : 

Hydroxide,  Ra(OH)2.       Chloride,  RaCl2;  RaCl2.2H20. 
Carbonate,  RaCO3.  Bromide,  RaBr2;  RaBr2.2H20. 

Nitrate,  Ra(N03)2. 

B.  Characteristics.  The  exceeding  rarity  of  the  com- 
pounds of  radium  has  rendered  impossible  any  extensive 
study  of  their  chemical  characteristics.  Their  behavior, 
however,  is  very  similar  to  that  of  the  barium  compounds. 
The  chloride  is  described  as  a  grayish-white  powder,  less 
soluble  in  water  and  in  dilute  hydrochloric  acid  than  is 
the  chloride  of  barium.  The  bromide  gives  off  bromine  in 
the  air,  and  becomes  alkaline  because  of  the  formation  of 
the  hydroxide.  The  hydroxide  absorbs  carbon  dioxide  and 
becomes  the  carbonate,  which  is  insoluble.  Salts  of  radium 
color  the  flame  carmine. 

Certain  physiological  effects  of  radium  compounds  are 
of  interest.  By  exposure  to  radium  rays  the  skin  is  burned, 
bacteria  are  destroyed  or  hindered  in  development,  plants 
lose  their  chlorophyll,  and  seeds  their  power  of  germination. 

Radium  is  a  disintegration  product  of  uranium,  and  is 
formed  directly  from  ionium.  It  is  found  in  all  uranium 
minerals,  and  in  the  older  minerals  the  amount  present 
is  directly  proportional  to  the  amount  of  uranium  in  the 


THE   RADIO-ELEMENTS. 


33 


mineral,  one  part  of  radium  being  associated  with  approx- 
imately three  million  parts  of  uranium.  Radium  salts  have 
been  found  to  emit  heat  at  a  rate  corresponding  to  about 
132  gram  calories  per  hour  per  gram  of  radium,  and  are 
thus  able  to  maintain  their  temperature  considerably  above 
that  of  their  surroundings. 

Pure  radium,  free  from  its  disintegration  products,  gives 
out  only  a  rays,  but  owing  to  the  presence  of  these  products, 
ordinary  radium  salts  emit  all  three  types  of  radiation.  The 
rate  of  disintegration  of  radium  corresponds  to  the  trans- 
formation of  about  forty-one  one-hundred  thousandths  of 
its  mass  per  year,  and  the  time  required  for  exactly  half  of 
any  given  quantity  to  completely  disintegrate  into  other 
elements  is  about  1670  years.  One  of  the  non-radicactive 
products  of  the  disintegration  of  radium  is  the  rare '  gas 
helium,  which  is  formed  from  the  expelled  a  particles, 
and  the  final,  stable  form  of  matter  ultimately  attained  after 
the  series  of  radioactive  changes  is  an  isotope  of  ordinary 
lead  known  as  uranio-lead,  having  an  atomic  weight  of  about 
206. 

Radium  Products.  Seven  successive  radioactive  dis- 
integration products  of  radium  have  been  identified.  The 
first  product  formed  is  a  gaseous  element  known  as  the 
emanation,  which  is  incapable  of  entering  into  chemical 
combination,  and  in  this  respect  is  similar  to  argon  and 
helium.  It  disintegrates  rather  rapidly,  forming  solid 
active  products  which  are  deposited  on  the  walls  of  a  vessel 
containing  the  emanation,  or  on  the  surface  of  any  object 
with  which  it  is  in  contact,  in  this  manner  giving  rise  to  the 
phenomenon  known  as  "  induced  "  or  "  excited  "  activity. 
The  emanation  is  condensed  at  the  temperature  of  liquid 
air  and  is  converted  into  a  gas  again  on  warming.  The  ema- 
nation has  been  found  to  give  a  characteristic  bright-line 
spectrum,  and  its  density  has  been  shown  to  correspond  to 
an  atomic  weight  of  about  222. 

The  products  of  radium  emanation,  taken  in  their  order 


34  THE  RARER  ELEMENTS. 

of  production,  are  known  as  radium  A,  B,  C,  d,  C2,  D,  E 
and  F.  Radium  D  is  commonly  called  "  radio-lead,"  from 
the  fact  that  it  is  separated  with  the  lead  from  uranium 
minerals  and  is  an  isotope  of  lead.  Radium  F  is  better 
known  as  polonium.  It  was  the  first  of  the  strongly  radio- 
active substances  to  be  identified,  and  was  discovered  in 
1898  by  P.  and  S.  Curie.  It  emits  only  a  rays  and  is  half 
transformed  in  a  period  of  136  days.  It  has  not  been 
obtained  pure  in  sufficient  quantity  to  make  a  determina- 
tion of  its  spectrum  or  atomic  weight  possible.  It  is  sepa- 
rated with  the  bismuth  from  uranium  minerals  and  exhibits 
a  chemical  behavior  similar  to  that  of  both  bismuth  and 
tellurium.  Radium  A  and  Ci  are  isotopic  with  polonium, 
Radium  B  with  lead,  Radium  C  and  E  with  bismuth,  and 
Radium  62  with  thallium. 


ACTINIUM,  Ac. 

The  radio-element  known  as  actinium  was  separated  from 
uranium  minerals  by  Debierne  in  1899.  It  has  not  yet  been 
possible  to  determine  either  its  spectrum  or  its  atomic 
weight.  Its  rate  of  transformation  is  also  unknown,  but  it 
is  probably  very  slow,  since  actinium  preparations  retain 
their  activity  unimpaired  for  considerable  periods.  Actin- 
ium is  apparently  a  disintegration  product  of  uranium 
and  occurs  in  exceedingly  small  proportions  in  all  uranium 
minerals.  It  is  separated  with  the  rare  earths  and  is  finally 
obtained  associated  with  the  lanthanum. 

Actinium  Products.  Seven  successive  radioactive  prod- 
ucts of  the  disintegration  of  actinium  have  been  identified. 
These  taken  in  their  order  are  radioactinium,  actinium  X, 
actinium  emanation,  actinium  A,  B,  C  and  D.  Actinium  A 
is  isotopic  with  polonium,  actinium  B  with  lead,  actinium  C 
with  bismuth  and  actinium  D  with  thallium.  Actinium 
emanation  is  a  gas,  apparently  inert  like  the  radium  emana- 
tion, and  similarly  condensed  at  the  temperature  of  liquid  air. 


THE  RADIO-ELEMENTS.  344 

THORIUM,  Th,  232.4. 

The  radioactivity  of  thorium  was  independently  dis- 
covered by  C.  G.  Schmidt  and  Mme.  Curie  in  1898.  The  rate 
of  transformation  of  thorium  has  not  yet  been  definitely 
determined,  but  it  is  undoubtedly  slower  even  than  that 
of  uranium.  According  to  Hahn  the  disint°gration  of 
thorium  is  accompanied  by  the  expulsion  of  a  particles,  but 
ordinary  thorium  salts  containing  disintegration  products 
of  thorium  emit  all  three  types  of  radiation. 

Thorium  Products.  Ten  successive  radioactive  disin- 
tegration products  of  thorium  have  been  identified.  These 
taken  in  the  order  of  their  production  are  known  as  meso- 
thorium  i,  mesothorium  2,  radiothorium,  thorium  X,  eman- 
ation, thorium  A,  thorium  B,  thorium  C,  thorium  C2  and 
thorium  D.  Mesothorium  i  and  thorium  X  have  chemical 
properties  similar  to  radium  and  are  isotopic  with  this 
element,  while  radio-thorium  and  thorium  are  isotopes.  The 
thorium  emanation,  like  the  other  emanations,  exhibits  the 
characteristics  of  an  inert  gas  of  the  argon  family,  and  is 
condensed  at  the  temperature  of  liquid  air.  Of  the  other 
thorium  products  mesothorium  2  is  an  isotope  of  actinium, 
thorium  A  of  polonium,  thorium  B  of  lead,  thorium  C  of 
bismuth,  thorium  C^  of  polonium  and  thorium  D  of  thal- 
lium. 

References:  Radioactive  Substances  and  their  Radiations,  by  E.  Rutherford, 
Cambridge  Univ.  Press,  1913;  The  Chemistry  of  the  Radio-Elements,  by  F.  Soddy, 
Longmans,  Green  and  Co.,  (second  edition)  1915. 


THE  RARER  ELEMENTS. 


TABLE  OF  RADIO-ELEMENTS. 

SHOWING  THE  TYPE  OF  RADIATION  EMITTED  BY  EACH  ELEMENT,  ITS  CONSTANT 
OF,  CHANGE,  AND  THE  TIME  REQUIRED  FOR  ONE-HALF  OF  ANY  GIVEN 
QUANTITY  TO  DISINTEGRATE  INTO  OTHER  FORMS  OF  MATTER. 


Name. 

Radiation 
emitted. 

.     Disintegration  Con- 

Half-value 
Period. 

a 
0 
0,7 
a 
a 
a 
a 
a 
ft 
a,  0,7 
a 

0 
0 
0 
a 
no  rays 
a 
a 
a 
a 
0 
a 
0,7 
a 
0 
0,7 
a 
a 
a 
a 
0 
13 
a 

ft 

1.3X10"!  °  (year).~.  A 
,  2.8XiQ-2  (dav)~  V 
'.i.oXicH3  (sec.)-y 

i.iXio~4  (year)/-1 
I.8XIO-1  (day)/-1 
3.8XIO-3  (sec.)/"1 
4.4Xio~4  (sec.)-1 
5.9Xio-"(sec^H-~ 

i.3Xio-3  (sec.)"1 
4.2X10    3(year)~1 
1.4X10"  l  ((day)"1 
5.  i  X  to-  3  (day)-1 

3.5  X  io-2,  (day)  -i 
6.  i  X  io-  J  (day)"1 
i.SXio-;1  (sec.)-1 

3.2Xio/-«  (sec.)-1 

ssXxflH(8efcx-1 

i.SXiA-'tsec,)-1 

I.2XIO"1  (year)"1 
3.  i  X  io-  •  (sec.)"1 
9.4X10-*  (day)"1 
2.2Xio~6  (sec.)^1 
i/3Xio-2(sec.)-i 

S.o     (sec.)"1 
i.SXio-Msec.)"11, 
/  1.9X10-*  (sec.)-1  \ 

3.  8  X  io-  3  (sec.)-1 

5-3  Xio9  years 
24  days 
1.14  min. 
2X10"  years? 

1670  years 
3-8  days 
3  minutes 
26  minutes 
19  minutes 
very  short 
indeed 
1.3  minutes 
1  6  years 
5  days 
136  days 
? 
19.5  days 
ii  days 
3.9  seconds 
0.002  second 
36  minutes 
2.1  minutes 
4.6  minutes 
i.8Xio10years 
5-5  years 
6.2  hours 
737  days 
3.6  days 
54  seconds 
0.14  second 
10.6  hours 
60  minutes 
exceedingly 
short 
3.1  minutes 

Uranium  X2  
Uranium  2  
Ionium  
Radium  
Radium  emanation  

Radium  B  
Radium  C  
Radium  Ci  

Radium  C2  
Radium  D  
Radium  E. 

Radium  F 

Radioactinium  
Actinium  X  
Actinium  emanation  .... 
Actinium  A  
Actinium  B  
Actinium  C  
Actinium  D. 

Thorium 

Mesothorium  i 

Mesothorium  2 

Radiothorium  
Thorium  X  
Thorium  emanation  
Thorium  A  
Thorium  B  
Thorium  C  
Thorium  Cj  

Thorium  D  

CHAPTER  IV. 

THE  RARE  EARTHS.* 

The  rare  earth  elements  may  conveniently  be  classified 
as  follows : 

I.  THE  YTTRIUM  GROUP,  consisting  of 

1.  Yttrium.  5.  Dysprosium. 

2.  Erbium.  6.  Ytterbium. 

3.  Holmium.  7.  Lutecium. 

4.  Thulium.  8.  Celtium. 
II.  THE  TERBIUM  GROUP,  consisting  of 

i.  Terbium. f  2.  Gadolinium. * 

3.  Europium.* 

III.  THE  CERIUM  GROUP,  consisting  of 

1.  Cerium.  4.  Praseodymium. 

2.  Lanthanum.  5.  Samarium. 

3.  Neodymium.  6.  Scandium.  § 

IV.  THORIUM. 
V.  ZIRCONIUM. 

The  rare  earths  occur  so  closely  associated  that  it  will  be 
advantageous  to  consider  their  occurrence  and  their  separa- 
tion before  taking  them  up  separately. 

Occurrence.|| — Mineral  sources  of  the  rare  earths  are  as 
follows : 

*  The  term  earth  is  applied  to  certain  metallic  oxides  which  were  formerly 
regarded  as  elementary  bodies,  as  Y2O3,  Er2Os,  LaoOs,  and  names  ending  in  a 
are  often  used  in  designating  them,  as  yttria,  erbia,  etc.  The  ending  urn  designates 
the  element,  as  yttrium,  erbium,  lanthanum. 

f  Placed  by  some  in  yttrium  group. 

\  Placed  by  some  in  cerium  group. 

§  According  to  Urbain  this  element  should  hardly  be  classed  among  the  rare 
earths  (Chem.  News  xc,  319). 

||  See  also  Schilling,  Das  Vorkommen  der  seltenen  Erden,  R.  Oldenbourg, 
Munchen,  1904. 

35 


THE  RARER   ELEMENTS. 


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THE  RARE  EARTHS. 


MINERAL  SOURCES  OF  THE  RARE  EARTHS—  Continued* 

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THE  R/fRER  ELEMENTS. 


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THE  RARE  EARTHS. 


39 


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THE  RARER    ELEMENTS. 


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Vietinghofite,  vid.  Samar 
Wiikitef  

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Yttrocrasite  

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THE  RARER  ELEMENTS. 


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0.01%.  Eberhard,  in  examination  of  over  350  minerals  and  rocks,  found  the  spectrum  of  scandium  (group  of  line 
3651.98,  with  brightest  at  3613.98)  rarely  absent.  He  mentions  wolframite,  cassiterite  and  monazite  especially.  (Sitzui 
1908,  851;  and  igio,  404.) 
NOTE.  By  the  study  of  cathodic  phosphorescence  applied  to  many  specimens  of  scheelites,  de  Rohden  observed  the 
Nd,  Pr,  Sm,  and  Tb  (Compt.  rend.  CLIX,  318). 

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1 

THE  RARE   EARTHS.  43 

Separation.  The  methods  of  separation  here  enumer- 
ated without  reference  to  original  sources  are  described  in 
full  in  Bohm's  "  Darstellung  der  seltenen  Erden,"  volume  i, 
pages  1 08  to  490. 

(1)  Ignition  of  the  nitrates,  carbonates,  or  oxalates,  and 

treatment  of  the  product  with  ammonium  nitrate, 
ammonium  chloride,  or  dilute  acid. 

(2)  Treatment  of  suspended  hydroxides  with  chlorine. 

(3)  Oxidation  with  potassium  permanganate. 

(4)  Treatment  with  peroxides,  as  PbO2,  etc. 

(5)  Oxidation  with  hydrogen  dioxide  or  sodium  dioxide. 

(6)  Treatment  with  persulphates. 

(7)  Treatment  with  the  electric  current.    (Vid.  also  (33).) 

(8)  Formation  of  basic  nitrates. 

(a)   By  treating  the  nitrates  with  oxides. 

(6)  By  treating  the  neutral  nitrates  with  hot  water. 

(9)  Formation  of  basic  chlorides. 

(a)   By  treating  the  chlorides  with  water. 

(6)  By  treating  the  chlorides  with  magnesium  oxide 

or  copper  oxide. 

(10)  Formation  of  basic  sulphates  by  the  action  of  water. 
(n)  Fractional  precipitation  with  ammonium  hydroxide. 

(12)  Fractional   precipitation   with   sodium   or  potassium 

hydroxide. 

(13)  Partial  precipitation  with  anilin. 

(14)  Precipitation  by  alkali  hyponitrides. 

(15)  Precipitation  by  sulphurous  acid  and  sulphites. 

(16)  Precipitation  by  sodium  thiosulphate. 

(17)  Precipitation  by  carbonates. 

(18)  Precipitation  as  chromates.* 

(19)  Precipitation  by  formates. 
(20).  Precipitation  by  acetates. 

(21)  Action  of  dilute  acid  upon  the  oxalates. 

(22)  Precipitation  as  the  sulphates. 

*  Vid.  James,  Jour.  Amer.  Chem.  Soc.  xxxvi,  638, 1418;  also  Egan  and  Balke, 
ibid,  xxxv,  376. 


44 


THE  RARER  ELEMENTS. 


(23)  Fractional  crystallization  of  the  nitrates. 

(24)  Action  of  alcohol  upon  the  nitrates. 

(25)  Action  of  (a)  acetylacetone,  (6)  ethylsulphate,  (c)  salts 

of  sulphanilic  acid. 

(26)  Fractional  crystallization  of  the  double  salts: 

(a)  Double  sulphates  with  alkali  sulphates. 

(b)  Double  nitrates  with  ammonium  nitrate. 

(c)  Double  nitrates  with  magnesium  nitrate. 

(d)  Double  nitrates  with  bismuth  nitrate. 

(e)  Double  fluorides  with  alkali  and  magnesium  fluo- 

rides. 

(27)  Action  of  (a)  neutral  or  acid  potassium  oxalate;  (b) 

ammonium  oxalate. 

(28)  Fractional   crystallization   of   the   bromates    (James, 

Jour.  Amer.  Chem.  Soc.  xxx,  182). 

(29)  Fractional   precipitation   of   the   succinates    (Lenher, 

Jour.  Amer.  Chem.  Soc.  xxx,  572). 

(30)  Action   of   ammonium   carbonate   upon   the   oxalates 

(James,  Jour.  Amer.  Chem.  Soc.  xxix,  495). 

(31)  Fractional  precipitation  by  potassium  stearate  (Stod- 

dart  and  Hill,  Jour.  Amer.  Chem.  Soc.  xxxm,  1076). 

(32)  Fractional  crystallization  of  the  picrates  (Dennis  and 

Bennett,  Jour.  Amer.  Chem.  Soc.  xxxiv,  7;    Dennis 
and  Rhodes,  ibid,  xxxvn,  807). 

(33)  Fractional  electrolysis  of  the  nitrates  and  the  chlorides 

(Dennis,  Lemon,  van  der  Meulen  and  Ray,  Jour. 
Amer.  Chem.  Soc.  xxxvn,  131,  1963;  XL,  174.) 

(34)  Fractional  precipitation   of   the   nitrites    (James   and 

Holden,  Jour.  Amer.  Chem.  Soc.  xxxvi,  1418). 

(35)  Fractional   solution   of   the   hydroxides   by   bromine 

(Browning,  Compt.  rend.  CLVIII,  1679). 

(36)  Fractional  precipitation  of  the  cobalticyanides  (James 

and  Bonardi,  Jour.  Amer.  Chem.  Soc.  xxxvn,  2645). 

(37)  Fractional  crystallization  of  the  dimethyl  phosphates 

(Jordan    and    Hopkins,    Jour.    Amer.    Chem.    Soc. 
xxxix,  2614). 


46  THE   RARER    ELEMENTS. 

(38)  Fractional  precipitation  of  the  glycolates  (Jordan  and 
Hopkins,  ibid.). 

The  separation  of  the  rare  earths  cannot  be  made  with 
quantitive  accuracy.  For  working  schemes,  however,  the 
student  is  referred  to  methods  worked  out  by  James  (Jour. 
Amer.  Chem.  Soc.  xxx,  979;  and  xxxiv,  757)  and  dia- 
grammatically  shown  on  pp.  216-18.  These  are  the  only 
schemes  of  separation  that  have  come  to  the  notice  of  the 
author,  and  they  are  followed  in  this  book  where  methods 
are  described  at  all  in  detail.  It  may  be  added  that  Urbain 
(Jour.  chim.  phys.  iv,  31)  has  arranged  the  rare  earths  ac- 
cording to  their  solubilities  as  follows :  lanthanum,  cerium, 
praseodymium,  neodymium,  samarium,  europium,  gado- 
linium, terbium,  dysprosium,  holmium,  yttrium,  erbium, 
thulium,  ytterbium. 

Urbain  has  used  the  magnetic  balance  successfully  as  a 
means  of  identification  and  also  as  a  test  for  purity  in  con- 
nection with  processes  of  fractionation.  The  oxides  are 
used  in  this  process,  and  the  coefficient  of  magnetization 
being  Xxio~6,  the  following  values  have  been  determined: 
Sc,  —0.05;  Y,—  0.14;  La,— 0.18;  Nd,  33.5;  Sm,  6.5;  Eu, 
33.5;  Gd,  161;  Tr,  237;  Dy,  290  (Compt.  rend.  CXLVII, 
1286;  CL,  913;  CLII,  141). 

I.  THE  YTTRIUM   GROUP, 
i.  YTTRIUM,  Y,   88.7. 

Discovery.  In  the  year  1794,  Gadolin  (Kongl.  Vet. 
Acad.  Handl.  xv,  137;  Crell  Annal.  (1796)  1,313)  discovered 
a  new  earth  in  a  mineral  later  called  Gadolinite,  which  had 
been  discovered  by  Arrhenius  and  described  by  Geyer  in  1788 
(Crell  Annal.  (1788)  1,229).  In  I797  Eckeberg  confirmed 
Gadolin's  discovery  and  named  the  new  earth  Yttria  (Kongl. 
Vet.  Acad.  Handl.  xvm,  156;  Crell  Annal.  (1799)  n,  63), 
deriving  the  name  from  Ytterby,  the  source  of  the  mineral. 

Occurrence.  Yttrium  occurs  always  in  combination.  Its 
chief  sources  are  the  minerals  gadolinite  and  xenotime,  and 


YTTRIUM.  <7 

monazite  residues  (vid.  Occurrence  of  Rare  Earths    pa^e 
35)- 

Extraction.  The  following  are  common  methods  for  the 
extraction  of  yttrium  salts  from  minerals : 

(1)  From  gadolinite  (or  any  other  silicate}.     The  finely 
powdered  mineral  is  mixed  with  common  sulphuric  acid  until 
the  mass  has  the  consistency  of  thick  paste.      It  is  then 
heated  until  dry  and  hard,  pulverized,  and  extracted  with 
cold  water.     From  this  extraction  the  oxalates  are  precipi- 
tated by  the  addition  of  oxalic  acid ;  they  are  then  washed, 
dried,  and  heated  at  400°  C.     The  oxides  thus  obtained  are 
dissolved  in  sulphuric  acid,  and  the  solution  is  saturated  with 
potassium  or  sodium  sulphate.     The  double  sulphates  of 
the  cerium  group  are  precipitated,  and  the  members  of  the 
yttrium  group  remain  in  solution. 

(2)  From  gadolinite.     The   mineral   is   decomposed  by 
aqua  regia  (vid.  Experiment  i). 

(3)  From  samarskite.     The  mineral  is  decomposed  by 
hydrofluoric  acid.     The  niobic  and  tantalic  acids  go  into 
solution,  and  the  yttrium  earths,  together  with  uranium 
oxide,  remain  (Lawrence  Smith,  Amer.  Chem.  Jour,  v,  44). 

The  Element.  A.  Preparation.  Elementary  "yttrium  may 
be  obtained  (i)  by  heating  the  chloride  with  potassium 
(Berzelius) ;  (2)  by  subjecting  the  melted  double  chloride  of 
sodium  and  yttrium  to  electrolysis  (Cleve,  Bull.  Soc.  Chim. 
d.  Paris  [2]  xvm,  193);  (3)  by  heating  the  oxide  with 
magnesium  (Winkler,  Ber.  Dtsch.  chem.  Ges.  xxni,  787). 

B.  Properties.  Yttrium  is  a  grayish-black  powder,  which 
decomposes  water  only  slightly  at  ordinary  temperatures, 
but  more  rapidly  on  boiling,  forming  the  oxide.  Ignited  on 
platinum  in  the  air,  it  burns  to  the  oxide  with  a  brilliant  light ; 
in  oxygen  with  a  very  intense  glow.  It  is  very  soluble  in 
dilute  acids,  including  acetic,  but  is  only  slightly  soluble  in  con- 
centrated sulphuric  acid.  It  decomposes  potassium  hydrox- 
ide at  the  boiling  temperature.  Its  melting-point  is  1490°  C. 

Compounds.  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  yttrium : 


48  THE  RARER  ELEMENTS. 

'  Oxide,  Y203. 
Hydroxide,  Y(OH)3. 

Carbonates,  Y2(CO3)3  +  3H2O;         Y2(CO3)3-Na2CO3  +  4H2O; 
Y2(C03)3-(NH4)2C03  +  2H20. 

Chlorides,    YC13;        YC13  +  6H2O;         YCl3.3HgCl2  +  9H,O; 

YCl3-2AuCl3+i6H20;  2YCl3-3PtCl2+24H2O. 

Chlorate,  Y(C103)3  +  8H20. 
Perchlorate,  Y(C1O4)3  +  8H2O. 
Bromides,  YBr3;  YBr3  +  9H2O. 
Bromate,  Y(BrO3)3  +  9H2O. 
Iodide,  YI3. 

lodate,  Y(I03)3  +  3H20. 
Periodate,  Y2O3-I2O7  +  8H2O. 
Fluoride,  YF3  +  o.sH2O. 

Nitrates,  Y(NO3)3  +  6H2O ;  2 Y2O3  -  3N2O5  +  9H2O. 
Cyanides,  YKFe(CN)6  +  2H2O;  Y(SCN)3  +  6H2O. 
Sulphates,  Y2(S04)3  +  8H2O ;  Y2(SO4)3  •  4K2SO4 ; 

Y2(SO4)3-Na2SG4+2H2O. 
Sulphite,  Y?(S03),  +  3H20. 
Seleniates,  Y2(SeO4)3  +  8H2O ;         Y2(SeO4)3  •  K2SeO4  +  6H2O ;, 

Y2(Se04)3-(NH4)2Se04  +  6H20. 
Selenites,  Y2(SeO3)3  +  1 2H2O ;  Y2O3  •  4SeO2  +  4H2O. 
Sulphide,  Y2S3. 
Oxalate,  Y2(C2O4)3  +  9H2O. 
Phosphates,  YP04;  Y(PO3)3;  YHP2O7  +  3.sH2O. 
Chromate,  Y2(CrO4)3-K?CrO4  +  *H2O. 
Tungstate,  Y2(WO4)3  +  6H2O. 
Carbide,  YC2. 
Organic  compounds,   md.  Platt   and   James,   Jour.  Amer.. 

Chem.  Soc.  xxxm,  i33o. 

B.  Characteristics.  The  compounds  of  yttrium  have- 
few  characteristic  reactions.  They  resemble  quite  closely 
the  compounds  of  aluminum,  but  yttrium  differs  from 
aluminum  in  having  a  hydroxide  insoluble  in  excess  of 


EXPERIMENTAL   WORK  ON  YTTRIUM.  49 

sodium  or  potassium  hydroxide  and  in  forming  no  alums. 
The  salts  of  yttrium  give  no  absorption  spectra.  Yttrium 
sulphate  differs  from  the  sulphate  of  cerium  in  forming 
no  insoluble  double  sulphate  with  potassium  or  sodium 
sulphate.  Most  of  the  rare  earth  compounds  except  the 
sulphate,  nitrate  and  halogen  salts  are  insoluble. 

Estimation.  Yttrium  is  generally  weighed  as  the  oxide, 
(Y2O3),  which  has  been  obtained  by  the  ignition  of  the 
hydroxide  or  the  oxalate  (vid.  James,  Jour.  Amer.  Chem. 
Soc.  xxxvi,  909). 

Separation.  In  the  course  of  analysis  the  yttrium  earths 
are  precipitated  with  the  aluminum  group.  They  may  be 
separated  from  aluminum  by  precipitation  with  oxalic  acid 
or  ammonium  oxalate  in  faintly  acid  solution;  in  this  re- 
action they  resemble  the  other  members  of  the  rare-earth 
group  (Ce,  La,  Pr,  Nd,  Th,  Zr,  etc.).  They  may  be  separated 
from  these  by  saturating  a  solution  of  the  sulphates  with 
potassium  sulphate ;  the  yttrium  earths  do  not  form  a  double 
sulphate  insoluble  in  potassium  sulphate  as  do  the  others. 

For  the  separation  of  yttrium  from  the  very  rare  mem- 
bers of  its  group  Methods  8,  9(0),  n,  18,  21,  28,  34  and  36 
(page  43)  have  been  used.  James  recommends  the  frac- 
tional crystallization  of  the  bromates  (28),  and  finds  the 
yttrium  in  the  fraction  between  the  holmium  and  the  erbium. 
Taking  the  fractions  free  from  holmium,  he  converts  them 
into  the  neutral  nitrates.  These  nitrates  of  yttrium  and 
erbium  are  boiled  with  the  addition  of  magnesium  oxide 
until  the  liquid  shows  no  absorption  bands  of  erbium. 


EXPERIMENTAL  WORK  ON  YTTRIUM. 

Experiment  i.  Extraction  of  yttrium  salts  from  gado- 
linite  (Be2FeY2Si2O10).  Warm  5  grm.  of  finely  powdered 
mineral  with  aqua  regia  until  it  is  completely  decomposed. 
Evaporate  on  a  water-bath  and  desiccate  to  remove  the 
silica.  Extract  with  hot  water  and  a  little  hydrochloric 


50  THE  RARER  ELEMENTS. 

acid,  and  add  to  the  extract  ammonium  oxalate  until 
precipitation  ceases.  Filter  off  the  precipitate,  which  con- 
sists of  the  oxalates  of  the  yttrium  and  cerium  groups,  to~ 
gether  with  traces  of  the  oxalates  of  manganese  and  cal- 
cium; dry  and  ignite.  Dissolve  in  a  small  amount  of 
hydrochloric  acid  the  oxides  thus  obtained,  and  saturate 
the  solution  with  potassium  sulphate*;  this  precipitates 
the  members  of  the  cerium  group  as  the  double  sulphates. 
Filter,  and  wash  with  a  solution  of  potassium  sulphate. 
From  the  filtrate  precipitate  the  yttrium  earths  by  an 
alkali  hydroxide  or  oxalate.  To  remove  the  manganese 
and  calcium,  dissolve  the  precipitate  in  nitric  acid,  evapo- 
rate to  dryness,  and  heat  until  the  manganese  salt  is  decom- 
posed. Extract  with  water,  filter  off  the  oxide  of  man- 
ganese, treat  the  filtrate  with  ammonium  hydroxide,  and 
stir  thoroughly.  The  calcium  hydroxide  will  be  dissolved, 
and  the  yttrium  earths  precipitated. 

Experiment  2.  Precipitation  of  yttrium  hydroxide 
(Y(OH)S).  (a)  To  a  solution  of  an  yttrium  salt  add  am- 
monium hydroxide. 

(6)  Repeat  the  experiment,  using  sodium  or  potassium 
hydroxide. 

Note  the  insolubility  in  excess  in  each  case. 

(c]  Precipitate  yttrium  hydroxide  by  the  action  of 
ammonium  sulphide. 

Experiment  3.  Precipitation  of  yttrium  carbonate 
(Y2(CO3)3).  (a)  To  a  solution  of  an  yttrium  salt  add 
ammonium  carbonate. 

(6)  Repeat  the  experiment,  using  sodium  or  potassium 
carbonate. 

Note  the  solubility  in  the  cold  upon  the  addition  of  an 
excess  of  the  alkali  carbonates,  and  the  reprecipitation 
on  boiling. 

(c)  Try  the  action  of  the  common  acids  upon  yttrium 
carbonate. 

*  Or,  with  sodium  sulphate  (James,  Jour.  Amer.  Chem.  Soc.  xxxv,  559). 


THE  YTTRIUM  GROUP.  51 

Experiment  4.  Precipitation  of  yttrium  oxalate 

(Y2(C2O4)3).  To  a  solution  of  an  yttrium  salt  add  a  solu- 
tion of  either  oxalic  acid  or  an  alkali  oxalate. 

Experiment  5.  Precipitation  of  yttrium  phosphates 
(Y2(HPO4)8;  YPOJ.  To  a  solution  of  an  yttrium  salt 
add  sodium  phosphate  in  solution  (Na2HPO4).  The  pre- 
cipitate is  said  to  be  of  the  acid  form  Y2(HPO4)3.  The 
neutral  phosphate  (YPO4)  is  formed  by  treating  an  yttrium 
salt  in  solution  with  an  ammoniacal  phosphate. 

Experiment  6.  Precipitation  of  yttrium  ferrocyanide 
(YKFe(CN)6).  To  a  solution  of  an  yttrium  salt  add  potas- 
sium ferrocyanide. 

Experiment  7.  Precipitation  of  yttrium  chr  ornate 
(*Ya(CrO4),-;yY2O8).  To  a  solution  of  an  yttrium  salt  add 
a  solution  of  potassium  chroma te,  and  neutralize  if  necessary. 

Experiment  8.  Precipitation  of  yttrium  fluoride  (YFs). 
To  a  solution  of  an  yttrium  salt  add  potassium  fluoride. 

Experiment  9.  Negative  tests  of  yttrium  salts.  Note 
that  hydrogen  sulphide  gives  no  precipitate  with  yttrium 
salts,  and  that  saturation  of  a  solution  of  an  yttrium  salt 
with  potassium  or  sodium  sulphate  gives  no  insoluble 
double  salt. 

2.  ERBIUM,  Er,  167.7  5-  DYSPROSIUM,  Dy,  162. 5 

3.  HOLMIUM,  Ho,  163.5  6.  YTTERBIUM,  Yb,i73.5 

4.  THULIUM,*  Tm,  168.5          7.  LUTECIUM,  Lu,  175 

8.  CELTIUM,  Ct. 

Discovery.  In  1843  Mosander  (J.  pr.  Chem.  xxx,  288) 
announced,  as  the  result  of  his  investigation  of  yttria,  its 
separation  into  three  earths,  two  white  and  one  yellow. 
To  the  less  basic  of  the  white  oxides  he  gave  the  name 
Terbium  earth,  to  the  more  basic  the  original  name  Yttrium 
earth,  and  the  yellow  oxide  he  called  Erbium  earth. 

In  1879  Cleve  (Compt.  rend.  LXXXIX,  478),  while  work- 

*  For  the  most  recent  work  upon  this  earth,  vid.  James,  Jour.  Amer.  Chem. 
.Soc.  xxxin,  1332,  1363. 


52  THE  RARER  ELEMENTS. 

ing  on  erbium  earth,  discovered  two  elements,  Holmium 
and  Thulium,  which  he  separated  as  the  oxides. 

Seven  years  later  Lecoq  de  Boisbaudran  (Compt.  rend, 
en,  1004),  announced  the  isolation  of  a  new  earth  from  the 
oxide  of  holmium,  namely,  that  of  Dysprosium. 

In  1878  Marignac  (Compt.  rend.  LXXXVII,  578)  found  in 
gadolinite  the  oxide  of  a  new  element  which  he  named 
Ytterbium. 

In  1906  Auer  von  Welsbach  (Monatshefte  f.  Chem. 
xxvn,  935)  announced  that  he  had  decomposed  ytterbium 
by  the  action  of  ammonium  oxalate  on  the  double  ammo- 
nium oxalate,  and  in  1907  Urbain  (Compt.  rend.  CXLV,  759; 
Chem.  News  xcvi,  271)  stated  that  by  subjecting  Marignac's 
ytterbium  to  fractional  crystallization  in  nitric  acid  he  had 
separated  it  into  two  elements,  which  he  called  Neoytter- 
bium*  and  Lutecium. 

Four  years  later,  while  subjecting  the  gadolinite  earths 
to  fractional  crystallization  in  nitric  acid,  Urbain  obtained 
a  mother  liquor  from  which  he  separated  an  oxide  of  very 
low  magnetic  susceptibility.  The  arc  spectrum  showed 
many  new  lines,  some  very  intense.  The  new  earth  proved 
to  be  in  chemical  character  between  lutecium  and  scandium. 
The  name  Celtium  was  proposed,  and  the  symbol  Ct 
(Compt.  rend.  CLII,  141;  Chem.  Ztg.  xxxv,  161). 

In  1899  Crookes  (Chem.  News  LXXIX,  212)  separated 
from  the  yttrium  earths  by  fractional  fusion  of  the  nitrates 
and  fractional  crystallization  of  the  oxalates  a  new  substance 
having  a  group  of  lines  in  the  ultra  violet.  This  substance 
he  at  first  called  Monium  and  later  Victorium  (Proc.  Royal 
Soc.  LXV,  237).  Urbain,  however,  considers  it  to  be  iden- 
tical with  gadolinium  (Jour.  chim.  phy.  iv,  321). 

Occurrence.  These  very  rare  earths  are  found  in  small 
quantities  and  varying  proportions  associated  with  yttria 
(vid.  Occurrence  of  Rare  Earths,  page  35).  Their  chief 

*  Now  known  as  ytterbium. 


THE  YTTRIUM  GROUP. 


53 


sources  are  as  follows :  of  erbium,  gadolinite,  yttrotantalite, 
euxenite,  sipylite,  xenotime;  of  ytterbium,  gadolinite, 
sipylite,  xenotime,  euxenite ;  of  holmium,  thulium  and  dys- 
prosium, gadolinite,  keilhauite,  euxenite,  samarskite. 

Extraction.  Methods  for  the  extraction  of  the  yttrium 
earths  have  been  already  given  (vid.  Extraction  of  Yttrium, 
page  46). 


Er 

Yb 

Oxides  

Er2O3 

Yb2O3 

Hydroxides  

Chlorides 

Er205 
Er,0(OH)4 

ErCl3 

Yb2Os+6H2O 
YbCl3  +  3H2O 

ErBr3  +  9H,O 

ErI, 

Fluoride  

ErF, 

Chlorate  
Perchlorate  

Er(ClO3)3  +  8H2O 
Er(ClO4)3  +  8H2O 
Er(BrO3)3  +  9H2O 

lodate  

Er(IOs)3  +  3H,O 

Sulphite  

Er2(SO3)3  +  3H2O 

Sulphates  
Double  sulphates  

Er2(S04)3  +  8H20 
Er2(SO4)3-3K2SO4 

Yb2(S04)3  +  8H2O 

Dithionate  

Kr2(S04V  sNa2S04 
Er2(S04)3.(NH4)2S04 
Er2(S2O6)3+i8H2O 

Selenites  

Er2(SeO3)3  -f  sH2O 

Yb,(SeCO. 

Seleniate      

Er2(SeO4)3+sH2O 

Nitrate 

Er(NO3)3  +  6H2O 

ErPO4  +  H2O 

Pvrophosphate  

Er,H2(P,CM2  +  7H2O 

Carbonate  

Er2O3-2CO2+2H2O 

Oxalates  

Er2(C2O4)3  +  1  2H2O 

Yb2(C2O  %  +  ioHjO 

Acetates  
Sulphide  

Er(C,H,Oi),  +  2H,0 
Er  Ss 

Yb(C2H302)3  +  2H20 

Compounds.  A.  Typical  forms.  In  the  table  on  this 
page  are  given  typical  compounds  of  erbium  and  ytterbium. 

B.  Characteristics.  In  general  chemical  behavior  the 
compounds  of  the  yttrium  earths  resemble  closely  those  of 
yttrium.  The  salts  of  erbium  are  of  a  rosy  tint  and  give 
absorption  bands.  The  oxide  is  yellowish.  Ytterbium 
forms  colorless  compounds  and  gives  no  absorption  bands. 
The  compounds  of  holmium,  thulium,  dysprosium,  lutecium, 


54 


THE  RARER  ELEMENTS. 


and  celtium  have  not  been  sufficiently  investigated  to 
warrant  description.  The  identification  of  members  of  this 
group  is  made  by  the  methods  of  spectrum  analysis. 

Separation.  For  the  separation  of  erbium  from  the 
other  members  of  the  yttrium  group  Methods  8,  9,  n,  12,  13, 
20,  2 6 (a),  and  28  (page  43)  are  used.  James  obtains  erbium 
by  his  bromate  process  (vid.  Separation  of  Yttrium,  page  49) 
in  the  fraction  between  yttrium  and  thulium. 

In  separating  ytterbium,  Methods  8,  9,  n,  21,  26(0),  and 
28  are  recommended.  In  the  bromate  process  this  earth  is 
to  be  found  in  the  mother  liquor  after  the  separation  of  the 
fractions  containing  the  other  members  of  the  group. 

Holmium  has  been  separated  by  Methods  i,  u,  13,  2 6 (a), 
and  28.  It  is  found  in  the  bromate  process  in  the  fraction 
between  dysprosium  and  yttrium. 

For  thulium  Methods  8,  25(6),  and  28  have  been  recom- 
mended. It  crystallizes  in  the  bromate  process  in  the  last 
fraction  following  the  erbium. 

Dysprosium  has  been  separated  by  Methods  n,  2 6 (a), 
and  28.  The  bromate  of  this  earth  crystallizes  between 
terbium  and  holmium. 

II.  THE  TERBIUM  GROUP. 

i.  TERBIUM,*  Tr,  159.2        2.  GADOLINIUM,  Gd,  15 7. 3 
3.  EUROPIUM,  Eu,  152. 

Discovery.  Terbium  was  first  isolated  by  Mosander  in 
1843  (rid-  Discovery  of  Erbium). 

In  1886  Marignac  and  Lecoq  de  Boisbaudran  (Compt. 
rend,  en,  902)  separated  from  terbium  earth  the  oxide  of  an 
unknown  element  named  by  them  Gadolinium. 

Demarcay,  in  1901  (Compt.  rend,  cxxxn,  1484),  isolated 
a  colorless  earth  closely  associated  with  samarium,  and 
named  the  new  element  Europium.  This  earth,  the  exist- 

*For  review  of  recent  work  vid.  James,  J.  Amer.  Chem.  Soc.  xxxm,  816; 
xxxvi,  2060;  xxxvii,  2652;  xxxvin,  873. 


THE  TERBIUM  GROUP. 


55 


ence  of  which  had  for  some  years  been  recognized  by  him- 
self and  by  others,  had  been  designated  by  him  as  2,  and  by 
Lecoq  de  Boisbaudran  as  Ze. 

Occurrence.  These  earths  are  found  in  small  quantities 
associated  with  the  yttrium  earths  (vid.  Occurrence  of  Rare 
Earths,  page  35).  The  chief  sources  of  terbium  are  gado- 
linite,  samarskite,  euxenite,  and  monazite;  of  gadolinium, 
samarskite  and  orthite;  of  europium,  samarskite,  orthite, 
cerite,  gadolinite,  keilhauite. 

Extraction.  These  earths  are  extracted  from  minerals 
with  the  members  of  the  yttrium  group  (vid.  Extraction  of 
Yttrium,  page  46) . 

Compounds.  A .  Typical  forms.  The  following  are  typ- 
ical compounds  of  terbium  and  gadolinium : 


Tr 

Gd 

Oxide        

Tr2O3 

Tr2O3  +  6H2O 

Chloride 

GdCI3  +  6H2O 

Bromide  

GdBr3  +  6H2O 

Sulphate  

Tr,(s64j,  +  8H,6 

Gd,(SO4)3-  K2SO4  +  2H2O 

Nitrates  

Tr(NO3)3  +  6H2O 

Gd(XO3)3  +  5H2O 

2Gd(XO3)3  •  3Ni(NO3)-  +  24HjO 

Carbonates  

Tr2(CO3)3  +  #H2O 

Gd2(CO3)3+i3H2O 

Acetates  

Tr(C2H3Oj)3 

Gd(C2H3O2)3  +  4H2O 

B.  Characteristics.  The  compounds  of  the  terbium 
earths  are  very  similar  in  chemical  form  and  behavior  to 
those  of  the  yttrium  earths.  The  members  of  this  group  are 
distinguished  from  the  yttrium  earths  on  the  one  hand,  and 
from  the  cerium  earths  on  the  other,  in  that  their  double 
potassium  sulphates  are  more  insoluble  in  a  saturated  solu- 
tion of  potassium  sulphate  than  the  corresponding  salts  of 
the  former  group,  and  less  insoluble  than  those  of  the  latter. 

Separation.  Methods  8,  n,  18,  19,  26  (a),  and  28  (page 
43)  have  been  used  in  separating  terbium  from  other  rare 
earths.  James  separates  terbium  from  the  cerium  earths 


56  THE  RARER  ELEMENTS. 

by  saturation  with  sodium  sulphate.  On  conversion  of  the 
yttrium  earths  together  with  terbium  into  the  bromates, 
and  crystallization,  the  terbium  separates  in  the  first  frac- 
tion. Gadolinium  has  been  separated  by  Methods  n,  23, 
26  (a),  (&),  (V),  (d),  29,  37  and  38.  James  classifies  it  in  the 
cerium  group,  and  by  crystallization  of  the  double  magnes- 
ium nitrates  separates  it  in  the  last  fraction. 

Methods  26  (c)  and  (d)  have  been  especially  effective  in 
separating  europium.  James  finds  the  main  portion  of  the 
europium  with  the  cerium  earths,  especially  samarium,  after 
the  treatment  with  sodium  sulphate.  When  lanthanum, 
praseodymium,  neodymium,  samarium,  europium,  and  gado- 
linium are  subjected  to  fractional  crystallization  as  the 
double  magnesium  nitrates,  europium  appears  in  the  last 
fraction  before  gadolinium  and  following  samarium. 

III.  THE   CERIUM   GROUP. 
i.  CERIUM,  Ce,  140.25. 

Discovery.  In  the  course  of  the  analysis  of  a  mineral 
from  Riddarhyttan,  Sweden,  in  1803,  Klaproth  discovered 
an  earth  which,  while  resembling  yttria  in  many  of  its 
reactions,  differed  from  it  in  being  insoluble  in  carbonate 
of  ammonium,  and  in  acquiring,  when  ignited,  a  light  brown 
color.  Because  of  this  latter  peculiarity,  the  name  Ochroite 
suggested  itself  to  him,  from  'coXpo?,  yellow  brown  (Phil. 
Mag.  xix,  95).  At  the  same  time,  and  independently  of 
Klaproth,  Berzelius  and  Hisinger  made  the  same  discovery. 
Their  name  for  the  new  element  was  Cerium,  chosen  in  honor 
of  the  discovery  of  the  planet  Ceres  by  Piazzi  in  1801  (Phil. 
Mag.  xx,  155;  xxn,  193). 

Occurrence.  Cerium  is  found  in  many  minerals,  asso- 
ciated, usually,  with  other  members  of  the  rare  earth 
group  (vid.  Occurrence  of  Rare  Earths,  page  35).  Its 
chief  sources  are  allanite,  monazite,  and  cerite. 

Extraction.  Cerium  is  generally  extracted  from  cerite 
through  decomposition  of  the  mineral  by  heating  it  with 
strong  sulphuric  acid  (vid.  Experiment  i).  The  decom- 


THE  CERIUM  CROUP.  57 

position  may  be  accomplished  also  by  the  action  of  a  mix- 
ture of  strong  hydrochloric  and  nitric  acids,  but  better 
results  may  be  expected  by  the  former  method. 

The  Element.  A.  Preparation.  Elementary  cerium  may 
be  obtained  (i)  by  reducing  the  chloride  with  sodium  or 
potassium  (Mosander) ;  (2)  by  subjecting  the  double  chloride 
of  cerium  and  sodium  to  electrolysis  (Pogg.  Annal.  CLV,  633). 

B.  Properties.  In  appearance  cerium  resembles  iron. 
While  fairly  stable  in  dry  air,  it  oxidizes  quickly  in  moist  air. 
It  takes  fire  more  easily  than  magnesium,  and  melts  at  a 
lower  temperature  than  silver  and  at  a  higher  temperature 
than  antimony.  It  is  soluble  in  dilute  acids,  but  is  not 
attacked  by  concentrated  sulphuric  or  nitric  acid.  It  com- 
bines with  chlorine,  bromine,  and  iodine,  forming  salts.  Its 
specific  gravity  is  7,  and  its  melting-point  640°  C.  It  forms 
alloys  with  iron,  aluminum,  zinc,  and  magnesium,  and  com- 
bines with  boron  and  silicon.  Many  of  these  alloys  are 
pyrophoric  (vid.  Levy,  Rare  Earths,  p.  314). 

Compounds.  A.  Typical  forms.  The  following  are  typ- 
ical forms  of  the  two  classes  of  cerium  compounds : 

Oxides Ce2Oj  CeO2 


Hydroxides.  .  .  . 

.Ce2O3-6H20 

2Ce02.3H20 

Carbonates  

.Ce2(C03)3+5H20 

Ce(C03)2+o.5H20 

Chloride  

.CeCl3 

Bromide  

.CeBr3 

Iodide  

.CeI3 

Perchlorate  

.Ce(C104)3+8H20 

Bromate  , 

.Ce(Br03)3+9H20 

lodate  

.Ce(I03)3+2H20 

Fluorides  

.CeF3 

CeF.+  HjO 

Cyanide  

.Ce(CN)3 

Ferrocvanides.  . 

.Ce4(FeC6N6)3+3oH20 

CeKFeC,N,+  3H2O 

Ferricyanide.  .  .  . 

.CeFeC6N6+8H20 

Sulphocyanide  . 

.  Ce(CSN)3+  yH2O 

Sulphide Ce2S3 

Sulphite Ce2(S03)3+  3H2O 

Sulphates Ce2(S04)3+  3>  5,  6,  8,  9,  and      Ce(SO4)2  +  4H2O 


58  THE  RARER  ELEMENTS, 

Double  sulphates.  Ce2(SO4)3  •  3K2SO4+  2H2O        Ce(SO4)2  •  2K2SO4+  aH2O 

Ce2(SO4)3-  Na2SO4+  2H2O 

Ce2(S04)3  •  (NH4)2S04+  8H2O 

Nitrates Ce(NO3)3+  6H2O  Ce(NO3)4 

Double  nitrates.  .Ce2(NO3)6-  3Zn(NO3)2+  2Ce(NO3)4-4KNO3+  3H2O 

24H20 

Ce2(NO,V3Co(NO,)2+  2Ce(NO3)4.4(NH4)NO3+ 

24H2O,  etc.  3H2O 

Phosphates CePO4  (CeO2)4  •  (P2O5)«+  26H2O 

Oxalate Ce2(C2O4), 

Carbide CeC2 

B.  Characteristics.  Cerium  exists  in  compounds  in  two 
conditions  of  oxidation.*  The  higher  or  eerie  salts  are 
easily  reduced  to  the  lower  or  cerous  condition  by  the. 
ordinary  reducing  agents  (e.g.  H2S,  S03,  H2C2O4,  etc.), 
and  the  cerous  salts  may  be  oxidized  to  the  eerie  condition 
by  oxidizing  agents  (e.g.  PbO2  +  HN03,  H2O2  in  alkaline 
solution,  KMnO4,  etc.).  In  general  the  cerous  salts  are 
colorless,  and  the  eerie  yellow.  The  lower  oxide  of  cerium, 
(Ce20s),  on  ignition  goes  over  to  the  higher  condition, 
(Ce02).  The  cerous  salts  are  the  more  stable,  and  con- 
sequently they  form  the  greater  number.  They  resemble 
the  yttrium  salts  in  many  of  their  reactions,  and  are 
distinguishable  from  them  chiefly  by  the  greater  insolu- 
bility of  the  double  sulphates  with  sodium  sulphate  and 
potassium  sulphate  respectively  in  excess  of  the  alkali 
sulphate,  by  the  comparative  insolubility  of  the  carbonate 
in  ammonium  carbonate,  and  by  the  possibility  of  oxida- 
tion to  a  higher  condition.  Solutions  of  pure  cerium  salts 
give  no  absorption  bands. 

Estimation.  A.  Gravimetric.  Cerium  is  usually  deter- 
mined gravimetrically  as  the  dioxide,  (CeO2),  obtained  by 
the  ignition  of  the  hydroxide  or  the  oxalate  (vid.  James,  Jour. 
Amer.  Chem.  Soc.  xxxvi,  909). 


*  Meloche  has  prepared  derivatives  of  a  perceric  oxide  (CeOs),  namely,  the 
double  carbonate  (Ce2O4(CO3)2-4K2CO3-i2H2O)  and  the  acetate  (Jour.  Amer. 
Chem.  Soc.  xxxvn,  2338,  2645). 


CERIUM.  59 

B.  Volumetric,  (i)  When  eerie  oxide,  (CeO,),  is  treated 
with  hydrochloric  acid  in  the  presence  of  potassium 
iodide,  iodine  is  set  free,  according  to  the  following 
equation  : 

2CeO2  +  8HC1  +  2KI  =  2CeCl3  +  4H2O  +  2KC1  +  12. 

The  iodine  may  be  estimated  in  acid  solution  by  stand- 
ard thiosulphate,  or  in  alkaline  solution  by  standard 
arsenious  acid  (Bunsen,  Ann.  Chem.  Pharm.  cv,  49;  Brown- 
ing, Amer.  Jour.  Sci.  [4]  vm,  451). 

(2)  When  cerium  oxalate  is  dissolved  in  sulphuric  acid 
the  oxalic  acid  may  be  readily  determined  by  potassium 
permanganate,   and  the  amount  of   cerium  present  may 
be  thus  estimated  (Stolba,  Zeitsch.  anal.  Chem.  xix,  194; 
Browning,  Amer.  Jour.   Sci.   [4]  vm,   457). 

(3)  When   yellow  eerie   compounds   are   treated   with 
hydrogen   dioxide  in  acid   solution,   they  are  reduced  to 
cerous  compounds,  with  bleaching  of  color  '(Knorre,  Zeitsch. 
angew.  Chem.  (1897),  685): 


(4)  Cerium  may  be  estimated  in  the  presence  of  the 
Other  rare  earths  by  precipitating  the  hydroxide  in  the  pres- 
ence of  potassium  ferricyanide,  filtering,  and  estimating  by 
potassium  permanganate  the  ferrocyanide  formed  (Browning 
and  Palmer,  Amer.  Jour.  Sci.  xxvi  (1908),  83),  according 
to  the  equations: 

(1)  2K3FeC6N6  +  Ce203  +  2  KOH 
2Ce02*. 

(2)  5K4FeC6N6+KMn04+4H2S04 
+MnS04+4H2O. 

Separation.  Cerium  falls  into  the  analytical  group 
with  aluminum,  iron,  etc.  Together  with  the  other  rare 


60  THE  RARER  ELEMENTS.  } 

earths  it  may  be  separated  from  these  by  oxalic  acid  or 
oxalate  of  ammonium.  For  separation  from  the  yttrium 
earths,  vid.  page  49. 

Cerium  may  be  separated  from  lanthanum,  praseodym- 
ium, and  neodymium  by  the  following  methods:  (i)  by 
treating  the  hydroxides  suspended  in  a  solution  of  caustic 
potash  with  chlorine  gas  (Mosander,  J.  pr.  Chem.  xxx, 
267),  or  with  liquid  bromine  (Browning  and  Roberts, 
Amer.  Jour.  Sci.  xxix,  45)  ;  (2)  by  boiling  a  solution  of  the 
nitrates  with  potassium  bromate  in  presence  of  a  lump  of 
marble,  thus  precipitating  basic  eerie  nitrate  (James  and 
Pratt,  Jour.  Amer.  Chem.  Soc.  xxxui,  1326)  ;  (3)  by  treating 
a  solution  of  the  cerium  earths  with  sodium  peroxide  and 
boiling  (O.  N.  Witt,  Chem.  Ind.  (1896),  n,  19)  ;  (4)  by  treat- 
ing the  oxalates  of  the  cerium  earths  with  warm  dilute 
nitric  acid,  thus  separating  the  cerium  as  basic  nitrate 
(Auer  von  Welsbach,  Monatshefte  f.  Chem.  v,  508);  (5) 
by  treating  a  solution  of  the  salts  with  hydrogen  dioxide  in 
the  presence  of  magnesium  acetate  (Meyer  and  Koss,  Ber. 
Dtsch.  chem.  Ges.  xxxv,  672);  (6)  by  treating  the  neu- 
tralized nitrate  solution  with  an  excess  of  zinc  oxide  and 
adding  potassium  permanganate,  thus  precipitating  cerium 
peroxide;  (7)  by  the  action  of  chromic  acid  on  the  hydroxides, 
dissolving  the  cerium  (Esposito,  Proc.  Chem.  Soc.  xxu,  20). 

From  thorium  cerium  may  be  separated  (i)  by  repeated 
precipitations  on  boiling  with  sodium  thiosulphate  (Fre- 
senius  and  Hintz,  Zeitsch.  anal.  Chem.  xxxv,  543)  ;  (2)  by 
boiling  with  potassium  trinitride  (Dennis  and  Kortright, 
Amer.  Chem.  Jour,  xvi,  79)  : 


(3)  by  boiling  a  nearly  neutral  solution  of  the  chlorides 
with  copper  and  cuprous  oxide  (Lecoq  de  Boisbaudran, 
Compt.  rend,  xcix,  525);  (4)  by  the  action  of  fumaric 


THE  CERIUM  GROUP.  6 1 

acid  in  40%  alcohol  upon  solutions  of  the  salts  in  40%  alco- 
hol (Metzger,  Jour.  Amer.  [Chem.  Soc.  xxiv,  901);  (5)  by 
oxidizing  cerous  salts  to  the  eerie  condition  and  treating 
with  ammonium  oxalate,  cerium  not  being  precipitated  at 
first  (Orlow,  Chem.  Ztg.  xxx,  733).  In  all  of  these  methods 
the  thorium  is  precipitated.  The  separation  from  thorium 
may  be  accomplished  also  by  electrolysis  of  the  nitrates 
(Dennis,  U.  S.  Patent,  i,  115,  513,  Nov.  1914). 

Cerium  is  separated  from  zirconium  by  fusion  of  the 
oxides  with  acid  potassium  fluoride,  and  extraction  with 
water  and  a  little  hydrofluoric  acid;  the  potassium  fluo- 
zirconate  is  dissolved,  and  the  thorium  and  cerium  remain* 
(Delafontaine,  Chem.  News  LXXV,  230). 

In  addition  to  the  foregoing,  Methods  i,  3,4,  6-10,  18, 
.and  26(6),  page  43,  have  been  used  in  separating  cerium 
from  its  associates. 

Experimental  Work.     Vid.  end  of  the  chapter. 

2.  LANTHANUM,  La,  139  5.  SAMARIUM,  Sm,  150.4 

3.  PRASEODYMIUM,  Pr,  140.9      6.  SCANDIUM,f  Sc.  44.1 

4.  NEODYMIUM,  Nd,  144.3 

Discovery.  In  1839  Mosander  found  that  when  the 
nitrate  of  cerium  had  been  ignited,  he  was  able  to  extract 
from  it  by  very  dilute  acid  an  earth  which  differed  in  prop- 
erties from  that  of  cerium,  while  from  the  portion  remain- 
ing undissolved  he  obtained  the  reactions  of  the  cerium 
earth.  He  supposed  the  unknown  substance  of  the  newly 
discovered  earth  to  be  an  element,  and  named  it  Lan- 
thanum, from  \avdaveiv,  to  hide  (Pogg.  Annal.  XLVI,  648; 
Liebig,  Annal.  xxxn,  235). 

*  For  the  action  of  organic  bases  as  precipitants  of  the  rare  earths,  md. 
Jefferson,  Jour.  Amer.  Chem.  Soc.  xxiv,  540;  Baskerville,  Science,  New 
Series,  xvi,  215;  Kolb,  J.  pr.  Chem.  [2]  LXVI,  59;  Allen,  Jour.  Amer.  Chem 
Soc.  xxv,  421;  Holmberg,  Chem.  Zentr.  1906,  II,  1595. 

t  Vid.  foot-note,  page  35. 


62  THE  RARER  ELEMENTS. 

In  1841,  while  engaged  in  further  work  upon  the  extrac- 
tion of  mixtures  of  cerium  and  lanthanum  oxides  by  dilute 
nitric  acid,  he  succeeded  in  separating  from  the  lanthanum 
oxide  another  earth,  rosy  in  color,  going  over  to  dark  brown 
on  being  heated.  Reserving  for  the  residual  oxide  the 
original  name  Lanthanum  earth,  he  called  the  base  of  the 
new  oxide  Didymium,  from  didvjjos,  twin, — a  name  sug- 
gested by  its  close  relationship  to  lanthanum  and  its 
almost  invariable  occurrence  with  it  (Pogg.  Annal.  LVI,  503). 

In  1885  Auer  von  Welsbach  announced  that  by  long- 
continued  fractional  crystallization  of  the  double  nitrates 
of  ammonium  with  lanthanum  and  didymium  in  the  pres- 
ence of  strong  nitric  acid,  he  had  separated  didymium 
into  two  elements  (Sitzungsber.  d.  k.  Acad.  d.  Wiss.  (1885) 
xcn,  Heft  I,  n,  317;  Ber.  Dtsch.  chem.  Ges.  xvin,  605). 
The  lanthanum  crystallized  out  first,  and  afterward  the 
decomposition  of  the  didymium  took  place.  To  these 
new  elements  he  gave  the  names  Praseodymium  (7rpd(rivos> 
leek-green}  and  Neodymium  (veos,  new). 

In  1878  Delafontaine  (Compt.  rend.  LXXXVII,  559,  632} 
announced  the  discovery  of  Decipium  in  a  North  Carolina 
samarskite. 

In  1879  Nilson  (Ber.  Dtsch.  chem.  Ges.  xn,  554),  while 
engaged  in  extracting  ytterbium  from  euxenite,  separated 
an  earth  of  much  lower  atomic  weight,  the  unknown  element 
of  which  he  called  Scandium.*  The  same  year  Lecoq  de 
Boisbaudran  (Compt.  rend.  LXXXVIII,  323),  in  the  course  of 
an  examination  of  the  absorption  spectra  of  the  earths 
separated  from  samarskite,  isolated  the  earth  of  another 
new  element,  Samarium. 

Occurrence.  The  cerium  earths  occur  closely  associated 
with  cerium.  The  following  are  some  of  the  chief  sources: 

*  The  discovery  of  scandium  was  predicted  by  Mendeleeff  in  1869  and  the 
hypothetical  element  was  named  Ekaboron.  To  it  he  gave  the  atomic  weight 
of  44,  and  he  described  the  properties  of  several  of  its  compounds. 


THE  CERIUM  GROUP.  63 

of  lanthanum,  cerite,  allanite,  monazite,  bastnaesite,  and 
lanthanite ;  of  praseodymium  and  neodymium,  cerite,  allan- 
ite, monazite,  and  bastnaesite;  of  samarium,  samarskite, 
orthite,  cerite,  gadolinite,  and  keilhauite;  of  scandium, 
gadolinite,  yttrotitanite,  euxenite,  and  keilhauite;  of  decip- 
ium,  samarskite. 

Extraction.  In  the  process  of  extracting  cerium  from 
cerite  (vid.  Experiment  i)  the  oxalates  of  the  cerium  earths 
are  precipitated  together. 

The  Elements.  I.  LANTHANUM.  A.  Preparation.  The 
element  lanthanum  may  be  obtained  (i)  by  reducing  the 
chloride  with  potassium;  (2)  by  subjecting  the  double 
chloride  of  lanthanum  and  sodium  to  electrolysis. 

B.  Properties.  Lanthanum  is  a  metallic  element  of  a 
lead-gray  color.  It  decomposes  cold  water  slowly  and  hot 
water  more  rapidly,  with  the  evolution  of  hydrogen.  It 
oxidizes  easily  in  the  air.  Its  specific  gravity  is  from  6.04 
to  6.19,  and  its  melting-point  is  810°  C. 

II.  PRASEODYMIUM    AND    NEODYMIUM.     The    elements 
praseodymium  and  neodymium  have  been  isolated  by  the 
electrolysis   of   the   anhydrous   chlorides    (Muthmann   and 
Weiss,  Liebig  Ann.  cccxxxi,  46).     Their  melting-points  are 
940°  C.  and  840°  C.,  respectively. 

III.  SAMARIUM  AND  SCANDIUM.     Samarium  has  been  ob- 
tained by  the  electrolysis  of  a  mixture  of  samarium  and 
barium  chlorides.     The  melting-point  of  samarium  is  1300°- 
1400°  C.     The  element  scandium  seems  not  to  have  been 
isolated. 

Compounds.  A.  Typical  forms.  In  the  table  on  the  next 
page  are  shown  typical  compounds  of  the  members  of  the 
cerium  group  other  than  cerium. 

B.  Characteristics.  The  compounds  of  the  other  mem- 
bers of  the  cerium  group  are  very  similar  to  those  of  cerium 
in  the  cerous  condition  in  their  behavior  toward  chemical 
reagents.  They  may  be  distinguished  from  the  compounds 
of  cerium  by  the  absence  of  yellow  color  on  the  addition  of 


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THE  CERIUM  GROUP.  65 

oxidizing  agents, — a  color  characteristic  of  the  higher  oxide 
of  cerium.  Lanthanum  may  be  distinguished  from  praseo- 
dymium and  neodymium  by  the  colorlessness  of  its  salts  and 
by  the  absence  of  an  absorption  spectrum. 

Praseodymium  salts  are  green.  While  their  chemical 
form  resembles  closely  that  of  the  neodymium  salts,  higher 
oxides  are  definitely  known  in  the  case  of  praseodymium. 
The  ordinary  oxide  Pr2Os  is  greenish  white;  the  higher 
oxide  Pr407  is  nearly  black.  Neodymium  salts  in  general  are 
of  a  rosy  color,  but  the  oxide  Nd2Os  is  bluish.  Each  of 
the  two  elements  has  distinctive  spectra,  spark  and  absorp- 
tion. The  lower  oxide  and  the  salts  of  samarium  are  yellow. 
Solutions  of  the  salts  give  characteristic  absorption  bands. 
The  oxides  and  salts  of  scandium  are  colorless.  The  salts 
show  no  absorption  spectrum. 

Estimation.  Like  cerium,  the  other  members  of  its 
group  are  generally  estimated  as  oxides,  obtained  by  ignition 
of  the  hydroxides  or  oxalates. 

Separation.  A.  Lanthanum  from  praseodymium  and  neo- 
dymium. Lanthanum  may  be  separated  from  praseodym- 
ium and  neodymium  (i)  by  dissolving  the  sulphates  in 
water  at  9°  C.  and  gradually  raising  the  temperature, — the 
lanthanum  sulphate  separating  first  (Hermann,  J.  pr.  Chem. 
LXXXII,  385);  (2)  by  heating  the  nitrates  at  4oo°-5oo°  C. 
and  extracting  with  water, — praseodymium  and  neodymium 
tending  to  form  an  insoluble  basic  nitrate  (Damour  and 
Deville,  Bull.  Soc.  Chim.  d.  Paris,  n,  339);  (3)  by  dissolving 
half  of  a  given  amount  of  the  oxides  in  warm  dilute  nitric 
acid,  then  adding  the  other  half  with  constant  stirring,  cool- 
ing the  mass,  and  extracting  with  water  (vid.  Experiment  i), 
— praseodymium  and  neodymium  being  found  in  the  residue 
(Auer  von  Welsbach,  Monatshefte  f.  Chem.  v,  508) ;  (4)  by 
fractional  crystallization  of  the  nitrates  with  magnesium 
nitrate, — the  lanthanum  appearing  in  the  first  crystal- 
lizations (James,  Jour.  Amer.  Chem.  Soc.  xxx,  979);  (5)  by 
treating  the  hydroxides  with  bromine  water, — the  lanthanum 


66  THE  RARER  ELEMENTS. 

being  the  more  soluble  (Browning,  Compt.  rend.  CLVIII, 
1679). 

Separation  Methods  i,  9,  n,  12,  17-23,  25(6),  and  26(0), 
(b),  and  (c),  page  43,  have  also  been  used  in  separating  lan- 
thanum. 

F  B.  Praseodymium  from  neodymium.  The  separation  of 
praseodymium  from  neodymium  may  be  accomplished  (i) 
by  making  several  hundred  fractional  crystallizations,  first 
of  the  nitrates  with  ammcnium  nitrate,  and  later  of  the 
nitrates  with  sodium  nitrate,  in  the  presence  of  lanthanum 
and  nitric  acid, — the  neodymium  salt  being  the  more  soluble 
(Auer  von  Welsbach,  Sitzungsber.  d.  k.  Acad.  d.  Wiss. 
(1885)  xcn,  Heft  I,  n,  317);  (2)  by  allowing  nitric  acid  to 
act  upon  the  oxalates, — the  praseodymium  salt  being  the 
more  soluble  (Scheele,  Ber.  Dtsch.  chem.  Ges.  xxxn,  417); 
(3)  by  treating  the  sulphates  with  water, — the  praseo- 
dymium sulphate  being  the  more  soluble  (Muthmann  and 
Rolig,  Ber.  Dtsch.  chem.  Ges.  xxxi,  1718);  (4)  by  making 
fractional  precipitations  of  a  solution  of  the  nitrates  by 
means  of  sodium  acetate  and  hydrogen  peroxide, — the 
praseodymium  separating  first  (Meyer  and  Koss,  Ber.  Dtsch. 
chem.  Ges.  xxxv,  676) ;  (5)  by  making  fractional  crystalliza- 
tions of  the  nitrates  with  magnesium  nitrate, — the  praseo- 
dymium appearing  first  after  the  lanthanum  (vid.  (4),  Sepa- 
ration of  Lanthanum  from  Praseodymium  and  Neodymium) . 
Methods  i,  8(a),  9,  n,  12,  19,  22,  23,  and  26(0),  page  43, 
have  also  been  used  in  the  separation  of  praseodymium 
and  neodymium  from  their  associates  and  from  each 
other. 

Samarium,  together  with  gadolinium  and  europium,  is 
found  by  James  in  the  mother  liquors  obtained  during  the 
fractionation  of  the  nitrates  of  lanthanum,  praseodymium, 
and  neodymium  with  magnesium  nitrate.  Urbain  and 
Lacomb  (Compt.  rend,  cxxxvn,  792,  and  cxxxvm,  84) 
have  found  that  the  addition  of  bismuth-magnesium  nitrate 
helps  in  the  separation.  The  samarium  appears  in  the  least 


EXPERIMENTAL  WORK  ON  THE  CERIUM  GROUP.  67 

soluble  fractions.     Vid.  also  Methods  9,  n,  20,  23,  and  26(0), 
(6),  and  (d),  page  43. 

Scandium  is  obtained  with  ytterbium  by  James  in  the 
mother  liquors  from  the  bromate  crystallizations  (vid.  dia- 
gram, page  216).  It  is  separated  from  ytterbium  by  pre- 
cipitation as  the  double  potassium  sulphate.  Vid.  also 
Methods  8  and  21,  page  43. 


EXPERIMENTAL   WORK   ON    CERIUM,    LANTHA- 
NUM,   PRASEODYMIUM,   AND   NEODYMIUM. 

Experiment  i.  Extraction  of  salts  of  the  cerium  group 
from  cerite  or  monazite.  Treat  25  grm.  of  the  powdered 
mineral  with  common  sulphuric  acid  and  stir  until  the  mass 
has  the  consistency  of  thick  paste.  Heat  until  the  excess 
of  sulphuric  acid  is  removed.  Cool,  pulverize,  and  digest 
with  cold  water  until  no  further  precipitate  appears  upon 
the  addition  of  ammonium  oxalate  to  a  few  drops  of  the 
extract.  Pass  hydrogen  sulphide  into  the  solution  to  re- 
move traces  of  bismuth  and  copper.  Filter,  and  to  the 
nitrate  add  oxalic  acid  to  complete  precipitation  of  the 
oxalates  of  cerium,  lanthanum,  praseodymium,  and  neo- 
dymium.  Ignite  the  oxalates,  and  dissolve  in  hydrochloric 
acid  the  oxides  obtained.  To  the  solution  add  potassium 
hydroxide  until  the  precipitation  of  the  hydroxides  is  com- 
plete. Make  up  the  volume  of  the  liquid  in  which  the 
hydroxides  are  suspended  to  about  200  cm.3  Add  about 
5  grm.  of  potassium  hydroxide  to  insure  an  excess,  and 
pass  a  slow  current  of  chlorine  gas  through,  stirring  from 
time  to  time,  until  the  liquid  is  no  longer  alkaline  in  reaction 
and  the  precipitate  has  assumed  a  deep-yellow  color.*  By 
this  process  the  cerium  hydroxide  is  oxidized  to  the  dioxide, 

*  The  processes  of  James  and  Pratt,  which  use  potassium  bromate  and  marble, 
or  of  Browning  and  Roberts,  which  substitute  bromine  for  chlorine,  may  be  em- 
ployed for  the  separation.  Vid.  page  60. 


68  THE  RARER  ELEMENTS. 

which  remains  undissolved,  and  the  hydroxides  of  lan- 
thanum, praseodymium,  and  neodymium  are  dissolved. 
When  the  separation  is  complete,  a  portion  of  the  washed 
precipitate  dissolved  in  hydrochloric  acid  should  give  no 
evidence  of  the  presence  of  praseodymium  or  neodymium, — 
for  example,  no  absorption  spectrum  (vid.  Experiment  12). 
The  absence  of  these  elements  at  this  point  is  considered 
sufficient  evidence  of  the  absence  of  lanthanum.  To  the 
solution  containing  lanthanum,  praseodymium,  and  neo- 
dymium, add  oxalic  acid  until  precipitation  is  complete. 
Filter  off  the  oxalates,  wash,  dry,  ignite,  and  set  aside 
for  later  use  the  oxides  obtained.  (For  method  of  sepa- 
ration vid.  Experiment  13.) 

Experiment  2.  Reduction  and  oxidation  of  cerium 
compounds,  (a)  To  a  small  portion  of  the  carefully  washed 
cerium  dioxide  obtained  in  the  previous  experiment  add 
a  little  hydrochloric  acid  diluted  with  an  equal  volume 
of  water  and  boil.  Note  the  evolution  of  chlorine  and 
the  ultimate  colorless  solution  of  cerium  chloride,  (CeCl3). 

(6)  To  a  portion  of  the  solution  obtained  in  (a)  add 
a  few  drops  of  ammonium  hydroxide  in  excess  and  some 
hydrogen  dioxide.  Note  the  orange  to  red-brown  precipi- 
tate (Ce03?).  Other  oxidizing  agents,  such  as  sodium  hypo- 
chlorite,  sodium  peroxide,  lead  dioxide,  potassium  per- 
manganate, etc.,  may  be  used.  Boil  the  solution  holding 
the  precipitate  in  suspension  and  note  that  the  deep-yellow 
color  changes  to  a  lighter  yellow.  The  precipitate  becomes 
essentially  the  dioxide,  (CeO2). 

(c)  To  another  portion  of  the  washed  cerium  dioxide 
from  Experiment  i  (2CeO2-3H2O)  add  hydrochloric  acid 
as  before,  and  also  a  crystal  of  potassium  iodide  in  the 
cold.  Note  the  liberation  of  iodine  according  to  the 
reaction  2CeO2  +  8HC1  +  2KI  -  2CeCl3  +  2KC1  + 12  +  4H,O. 

^Experiment  3.  Formation  of  eerie  nitrate,  (Ce(NO3)4). 
Dissolve  in  nitric  acid  a  portion  of  the  hydrated  eerie  oxide 
formed  in  Experiment  i.  Note  the  orange-red  color. 


EXPERIMENTAL  WORK  ON  THE  CERIUM  GROUP.  69 

Try  the  action  of  hydrogen  dioxide  and  oxalic  acid 
upon  separate  portions  of  the  solution. 

Experiment  4.  Precipitation  of  cerous  hydroxide, 
(Ce(OH)3).  (a)  To  a  solution  of  cerium  chloride  add 
sodium,  potassium,  or  ammonium  hydroxide  in  solution. 
Note  the  insolubility  of  the  hydroxide  in  excess  of  these 
reagents. 

(6)  Repeat  the  experiment  with  tartaric  acid  present 
in  the  solution. 

Experiment  5.  Precipitation  of  cerous  carbonate, 
(Ce2(CO3)3).  (a)  To  a  solution  of  cerium  chloride  add  a 
solution  of  sodium  or  potassium  carbonate.  Note  the 
comparative  insolubility  in  excess. 

(6)  Repeat  the  experiment,  using  ammonium  carbonate 
as  the  precipitant. 

(c)  Try  the  action  of  the  common  acids  upon  the  car- 
bonate of  cerium. 

Experiment  6.  Precipitation  of  cerium  oxalate, 
(Ce2(C2O4)3).  (a)  To  a  solution  of  a  cerium  salt  add  oxalic 
acid  or  an  oxalate.  Note  the  crystalline  character  of  the  pre^ 
cipitate,  especially  after  the  liquid  has  been  stirred  and  boiled. 

(b)  Try  the  action  of  hydrochloric  acid  upon  cerium 
oxalate. 

Experiment  7.  Precipitation  of  the  double  sulphate 
of  cerium  and  potassium  or  sodium,  (Ce2(SO4)3-3K2SO4  or 
Ce2(SO4),-NaaSO4).  To  a  few  drops  of  a  concentrated 
solution  of  a  cerous  salt  add  a  small  portion  of  a  saturated 
solution  of  sodium  or  potassium  sulphate. 

Experiment  8.  Precipitation  of  cerium  phosphate,  (CeP04) . 
(a)  To  a  solution  of  a  cerous  salt  add  sodium  phosphate  in 
solution. 

(b)  Try  the  action  of  hydrochloric  and  acetic  acids  upon 
separate  portions  of  the  precipitate. 

Experiment  9.  Precipitation  of  cerous  fluoride,  (CeFa). 
To  a  solution  of  cerium  chloride  add  potassium  fluoride  in 
solution. 


70  THE  RARER' ELEMENTS. 

Experiment  10.  Precipitation  of  the  ferrocyanide  of 
cerium  (Ce4(FeC6N6)3).  (a)  To  a  solution  of  cerium  chloride 
add  potassium  ferrocyanide. 

(6)  Note  that  potassium  ferricyanide  gives  no  precipi- 
tate. 

Experiment  1 1 .  Comparison  of  lanthanum,  praseodymium, 
and  neodymium  with  cerium,  (a)  Perform  Experiments  4 
to  10  inclusive  upon  dilute  solutions  of  salts  of  lanthanum, 
praseodymium,  and  neodymium. 

(6)  Note  that  pure  salts  of  these  elements  give  no  change 
of  color  with  oxidizing  agents.  Compare  with  cerium  salts 
(vid.  Experiment  2). 

Experiment  12.  Absorption  spectra.  Place  solutions  of 
salts  of  praseodymium  and  neodymium  between  the  slit 
of  the  spectroscope  and  a  luminous  flame.  Note  the  dark 
bands.  Observe  that  cerium  and  lanthanum  salts  in  solu- 
tion show  no  absorption  bands. 

Experiment  13.  Separation  of  praseodymium  and  neo- 
dymium. If  time  and  material  allow,  an  interesting  experi- 
ment may  be  performed  by  taking  about  100  grm.  of  the 
oxides  of  lanthanum,  praseodymium,  and  neodymium,  dis- 
solving them  in  a  known  amount  of  nitric  acid,  neutral- 
izing an  equal  amount  of  nitric  acid  by  means  of  magnesium 
oxide,  mixing  the  two  solutions,  and  proceeding  with  the 
fractional  crystallization  of  the  double  nitrates  to  the  point 
where  change  of  color  indicates  the  separation  of  praseo- 
dymium and  neodymium.  Observe  the  differences  in  the 
absorption  bands. 

Experiment  14.  Negative  tests  of  the  salts  of  cerium, 
lanthanum,  praseodymium,  and  neodymium.  Note  that 
hydrogen  sulphide  gives  no  precipitate  with  salts  of  this 
group.  Ammonium  sulphide  precipitates  the  hydroxides, 
not  the  sulphides. 


THORIUM. 


IV.  THORIUM.*   Th.  232.4. 

Discovery.  As  early  as  the  year  1818  Berzelius,  working 
on  a  mineral  from  Fahlun,  Sweden,  believed  that  he  had 
discovered  a  new  earth  (Annal.  der  Phys.  u.  Chem.  (1818) 
xxix,  247).  He  gave  it  the  name  Thoria,  from  Thor,  son 
of  the  Scandinavian  war  god  Odin.  Some  years  later,  how- 
ever, he  identified  the  supposed  new  earth  Pe  chiefly  a  basic 
phosphate  of  yttrium  (Pogg.  Annal.  iv,  145  .  In  1828  Es- 
mark  discovered,  near  Brevig,  Norway,  the  mineral  since 
known  as  thorite.  From  it  Berzelius  isolated  an  unknown 
earth ;  its  similarity  to  the  substance  described  by  him  some 
ten  years  earlier  prompted  the  name  Thoria  (Pogg.  Annal. 
xvi,  385). 

Occurrence.  Thorium  is  found  in  combination  in  cer- 
tain rare  minerals  (vid.  Occurrence  of  Rare  Earths,  page 
35).  Its  chief  sources  are  monazite,  thorianite,  and 
thorite. 

Extraction.  The  following  methods  may  be  used  for  the 
extraction  of  thorium  salts : 

(1)  From  thorite.     The  mineral  is  decomposed  by  heat- 
ing it   with   sulphuric   acid    (vid.    Cerium,    Experiment    i, 
page  67).     After  the  extraction  of  the  sulphate  with  cold 
water,  the  solution  is  heated  to   100°  C.  and  an  impure 
sulphate  of  thorium  comes  down.     By  repeated  solution  of 
the  precipitate  in  cold  water  and  reprecipitation  by  means 
of  heat  a  pure  sulphate  is  finally  obtained  (Delafontaine, 
Ann.  Chem.  Pharm.  cxxxi,  100). 

(2)  From  monazite.     (a)  The  mineral  is  decomposed  by 
sulphuric  acid  and  the  oxalates  are  precipitated  by  oxalic 
acid  (vid.  Experiment  i).     (b)  The  mineral  is  heated  in  an 
electric  furnace  with  about  an  equal  weight  of  petroleum 
coke  and  very  small  amounts  of  lime  and  fluorspar.     The 
phosphorus  distils,  the  lime  is  dissolved  out  by  water,  the 

*  For  a  discussion  of  radioactive  properties,  see  Chapter  III. 


72  THE  RARER  ELEMENTS. 

residue  is  dissolved  in  hydrochloric  acid,  and  the  thorium 
(ThO2)  is  separated  by  sodium  thiosulphate  (Baskerville, 
J.  Eng.  Ind.  Chem.  iv,  821). 

The  Element.  A.  Preparation.  Elementary  thorium 
"may  be  obtained  (i)  by  heating  the  chloride  with  metallic 
-sodium  (Zely  and  Hamburger) ;  (2)  by  reducing  the  double 
fluoride  of  potassium  and  thorium  with  potassium;  (3)  by 
-reducing  with  aluminum. 

B.  Properties.  Thorium  is  known  in  two  forms,  (i) 
that  of  a  grayish,  glistening  powder,  and  (2)  crystalline. 
It  is  stable  in  the  air,  and  does  not  decompose  water,  even 
at  100°  C.  When  heated  in  a  current  of  chlorine,  bromine, 
or  iodine,  it  glows  and  forms  the  salt.  It  is  soluble  in 
dilute  hydrochloric  and  sulphuric  acids,  in  concentrated 
sulphuric  acid  with  the  liberation  of  sulphur  dioxide,  and 
in  aqua  regia.  It  is  acted  upon  very  slowly  by  nitric 
acid,  and  is  not  attacked  by  the  alkali  hydroxides.  The 
specific  gravity  of  thorium  in  the  amorphous  condition 
is  10.97;  in  crystalline  form  11.2. 

Compounds.  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  thorium: 

Oxides,  ThO2;  Th2O7. 

Hydroxide,  Th(OH)4. 

Chlorides,  ThCl4;  also  double  salts  with  KC1  and  NH,C1. 

Oxychloride,  ThOCl. 

Bromide,  ThBr4. 

Iodide,  ThI4. 

Fluoride,  ThF4  +  4H2O. 

Chlorate,  Th(ClO3)4. 

Perchlorate,  Th(C104)4. 

Bromate,  Th(BrO3)4. 

lodate,  ThCIOg),. 

'Sulphide,  ThS2. 

'Oxysulphide,  ThOS. 

Su.phite,  Th(S03)2  +  H2O. 


THORIUM.  73 

Sulphates,  Th(SO4)2  +  9H2O;  also  double  salts  with  K2S04, 

Na2SO4;  and  (NH4)2SO4. 
Selenite,  Th(SeO3)2  +  H2O. 
Seleniate,  Th(SeO4)2  +  9H2O. 
Nitrate,  Th(NO3)4  +  i2H20. 
Borides,  ThB4,  ThB6. 
Phosphate,  Th3(PO4)4  +  4H2O. 
Pyrophosphate,  ThP2O7  +  2H2O. 
Hypophosphate,  ThP2O6. 
Ferrocyanide,  ThFe(CN)6+4H20. 
Silicide,*ThSi. 
Hydride,  ThH4. 
Nitride,  ThaN*. 
Carbide,  ThC2. 
Silicate,  ThSiO4. 

Carbonates,  Th(C03)2;  Th(C03)2-3Na2CO 
Oxalate,  Th(C2O4)2 


B.  Characteristics.  The  compounds  of  thorium  resem- 
ble in  chemical  form  those  of  cerium  in  the  eerie  con- 
dition. Thorium  resembles  cerium  also  in  having  a  hy- 
droxide insoluble  in  the  alkali  hydroxides,  and  in  forming 
a  double  sulphate  with  potassium  sulphate,  insoluble  in 
excess  of  that  precipitant.  The  salts  of  thorium  are  colorless 
except  where  the  element  is  combined  with  an  acid  having  a 
color  of  its  own.  They  are  in  general  insoluble,  with  the 
exception  of  the  chloride,  the  nitrate  and  the  sulphate. 
Possibly  the  most  distinctive  reactions  of  thorium  com- 
pounds are  the  ready  formation  of  a  soluble  double  oxalate 
when  ammonium  oxalate  is  added  in  excess  to  a  thorium 
salt  in  solution,  and  the  precipitation  of  the  hydroxide  when 
a  solution  of  a  thorium  salt  is  boiled  with  potassium 
hydronitride  (Dennis  and  Kortright,  Amer.  Chem.  Jour. 
xvi,  79). 

*  Honigschmidt,  Compt.  rend.  CXLH,  157;  CXLIH,  224. 


74  THE  RARER  ELEMENTS. 

Estimation.  Thorium  is  ordinarily  estimated  as  the 
oxide  (ThC>2),  obtained  by  ignition  of  the  hydroxide,  the 
nitrate,  or  the  oxalate. 

Separation.  Thorium,  together  with  the  rare  earths 
cerium,  yttrium,  zirconium,  etc.,  may  be  separated  from 
the  other  elements  by  oxalic  acid.  Methods  for  its  separa- 
tion from  yttrium  and  cerium  have  already  been  given 
(vid.  pages  49  and  60),  but  two  recent  methods  may  be  men- 
tioned here:  (i)  the  action  of  potassium  iodate  in  the  pres- 
ence of  nitric  acid  upon  rare  earth  solutions, — the  thorium 
salts  remaining  insoluble  even  on  boiling  (R.  J.  Meyer, 
Ztsch.  f.  anorg.  Chem.  LXXI,  65),  a  method  especially 
recommended  for  separations  from  scandium;  (2)  the 
action  of  sebacic  acid  on  rare  earth  solutions, — the  thorium 
sebacate  being  precipitated  (Smith  and  James,  Jour. 
Amer.  Chem.  Soc.  xxxiv,  281). 

From  zirconium  thorium  may  be  separated  (i)  by  the 
action  of  acids  upon  the  potassium  double  sulphates, — 
the  zirconium  salt  being  the  more  soluble;  (2)  by  the  action 
of  an  excess  of  hydrochloric  acid  upon  the  soluble  double 
ammonium  oxalates, — the  zirconium  remaining  in  solution; 
(3)  by  fusion  with  acid  potassium  fluoride;  (4)  by  the  action 
of  dimethylamine  upon  solutions  of  the  salts, — thorium 
hydroxide  being  precipitated  (Kolb,  J.  pr.  Chem.  [2]  LXVI, 
59) ;  (5)  by  electrolysis  of  the  nitrates  (Dennis,  U.  S.  Patent. 
1,115,513,  Nov.  1914). 

EXPERIMENTAL  WORK  ON  THORIUM. 

Experiment  i.  Extraction  of  thorium  oxide  from  mona- 
zite.  Treat  25  grm.  of  finely  ground  monazite  with  com- 
mon sulphuric  acid,  according  to  the  method  already 
described  (vid.  Experiment  i,  page  67).  Precipitate  the 
oxalates  with  oxalic  acid, — not  ammonium  oxalate, — boil 
and  filter.  Remove  the  oxalates  to  a  porcelain  dish,  ignite, 
and  dissolve  the  oxides  in  nitric  acid.  Evaporate  to  dryness 


EXPERIMENTAL   WORK  ON   THORIUM.  75 

to  remove  excess  of  acid,  dissolve  in  water,  and  precipitate 
thorium  thiosulphate  with  sodium  thiosulphate. 

Note.  This  method  may  be  employed  for  the  extraction 
of  thorium  from  discarded  Welsbach-light  mantles. 

Experiment  2.  Precipitation  of  thorium  hydroxide 
(Th(OH)4)  and  thorium  thiosulphate*  (Th(S2O3)2).  (a)  To 
a  solution  of  a  thorium  salt  add  sodium,  potassium,  or 
ammonium  hydroxide.  Note  the  insolubility  of  the  hy- 
droxide in  excess  of  the  precipitant. 

(6)  To  a  solution  of  a  thorium  salt  add  sodium  thio- 
sulphate in  solution  and  boil. 

Experiment  3.  Precipitation  of  thorium  carbonate,^ 
(Th (C03)2).  (a)  To  a  solution  of  a  thorium  salt  add 
potassium  or  sodium  carbonate.  Note  the  solubility  of 
the  precipitate  in  excess  and  the  reprecipitation  on  boiling. 

(b)  Repeat,  using  ammonium  carbonate. 

(c)  Note  the  solvent  action  of  the  common  acids  upon 
thorium  carbonate. 

Experiment  4.  Precipitation  of  the  oxalate  of  thorium, 
(Th(C2O4)2  +  2H2O).  (a)  To  a  solution  of  a  thorium  salt 
add  a  solution  of  oxalic  acid.  Note  the  insolubility  in 
excess  of  the  precipitant. 

(6)  Repeat,  using  ammonium  oxalate  as  the  precipitant. 
Note  the  solubility  in  excess,  especially  on  warming,  and 
the  reprecipitation  upon  the  addition  of  hydrochloric  acid. 

(c}  Try  the  solvent  action  of  ammonium  acetate  upon 
thorium  oxalate. 

Experiment  5.  Precipitation  of  the  double  sulphate 
of  potassium  and  thorium,  (Th(SO4)2-2K2SO4  +  2H2O  or 
Th(S04)2'-  4K2SO4  +  2H2O) .  Saturate  a  solution  of  a  thorium 
salt  with  potassium  sulphate.  (The  corresponding  sodium 
salt  (Th(SO4)2-Na2SO4  +  6H2O)  is  somewhat  soluble  in 
excess  of  sodium  sulphate.) 

Experiment    6.       Precipitation    of    thorium    phosphate, 

*  According  to  some  authors  this  precipitate  is  the  hydroxide, 
f  At  50°  C.  this  carbonate  is  said  to  become  basic. 


76  THE  RARER  ELEMENTS. 

(Th3(PO4)4+4H2O),  and  thorium  hypophosphate,  (ThP2O6). 
(a)  To  a  solution  of  a  thorium  salt  add  sodium  phosphate  in 
solution.  Orthophosphoric  acid  is  said  to  precipitate  an 
acid  phosphate  (ThH2(P04)2).  (6)  To  a  solution  of  a 
thorium  salt  add  sodium  hypophosphate  in  solution.  Note 
the  insolubility  of  the  precipitate  in  fairly  strong  hydro- 
chloric acid. 

Experiment  7.  Precipitation  of  thorium  fluoride, 
(ThF4  +  4H2O).  To  a  solution  of  a  thorium  salt  add  a 
solution  of  potassium  fluoride.  Double  salts  with  thorium 
fluoride  may  also  form  (#KF-/ThF4  typical). 

Experiment  8.  Precipitation  of  thorium  ferrocyanide, 
(ThFe(CN)6  +  4H2O).  To  a  solution  of  a  thorium  salt  add 
a  solution  of  potassium  ferrocyanide.  Note  the  absence 
of  precipitation  with  potassium  ferricyanide. 

Experiment  9.  Action  of  hydrogen  peroxide  upon  salts 
of  thorium.  To  a  solution  of  a  thorium  salt  add  a  little 
hydrogen  peroxide,  and  warm. 

Experiment  10.  Precipitation  of  thorium  iodate, 
(Th(IO3)4).  To  a  solution  of  thorium  nitrate  add  a  solu- 
tion of  potassium  iodate.  Note  the  insolubility  in  fairly 
strong  nitric  acid. 

Experiment  n.  Precipitation  of  thorium  sebacate.  To 
a  neutral  solution  of  a  thorium  salt  add  a  hot  solution  of 
sebacic  acid  (H2(CioHi8O4)),  and  boil. 

Experiment  12.  Negative  test  of  thorium  salts.  To  a 
solution  of  a  thorium  salt  add  hydrogen  sulphide.  Note 
that  ammonium  sulphide  precipitates  the  hydroxide,  not 
the  sulphide. 

V.  ZIRCONIUM,  Zr,  90.6. 

Discovery.  While  engaged  in  the  analysis  of  the  zircons, 
in  1788,  Klaproth  found  one  variety  containing  31.5%  of 
silica,  0.5%  of  the  oxides  of  iron  and  nickel,  and  68%  of  an 
earth  which  differed  from  all  earths  previously  known  to 
him.  He  observed  that  it  was  soluble  in  the  acids,  but 


ZIRCONIUM. 


77 


insoluble  in  the  alkalies,  in  the  latter  respect  differing  from 
alumina  (Ann.  de  Chim.  i,  238).  The  fact  that  zircon  was 
the  source  of  the  new  earth  suggested  the  name  Zirconium 
for  the  element. 

Occurrence.  Zirconium  is  found  combined,  widely  dif- 
fused, but  always  in  small  quantities  (vid.  Occurrence  of 
Rare  Earths,  page  35).  Its  chief  source  is  zircon. 

Extraction.  Zirconium  salts  may  be  extracted  from 
zircon  by  the  following  methods: 

(1)  The   finely   powdered   mineral   is   fused  with   acid 
potassium  fluoride   (vid.   Experiment   i)    (Marignac,  Ann. 
Chim.  Phys.  [3]  LX,  257). 

(2)  The   mineral   is   fused   with   potassium   bisulphate 
and  the  fused  mass  extracted  with  dilute  boiling  sulphuric 
acid.     The  basic  sulphate  (3ZrO2-SO3)  is  left  as  a  residue 
(Franz,  Ber.  Dtsch.  chem.  Ges.  n,  58). 

(3)  The  finely  powdered  mineral  is  heated  with  a  mix- 
ture of  sodium  hydroxide  and  sodium  fluoride,  the  mass 
is  cooled,  pulverized,  and  extracted  with  water.  The  residue, 
which  consists  mainly  of  sodium  zirconate,  is  digested  with 
hydrochloric  acid  until  dissolved.  After  the  solution  has 
been  evaporated  to  a  small  volume  the  zirconium  oxy- 
chloride  separates  in  crystalline  form  (Bailey,  Proc.  Royal 
Soc.  XLVI,  74). 

(4)  The  finely  powdered  mineral  is  fused  with  sodium  car- 
bonate, and  the  melt,  consisting  of  sodium  silicate  and 
sodium  zirconate,  is  extracted  with  water.  The  silicate 
dissolves  and  the  zirconate  is  hydrolyzed,  forming  zirco- 
nium hydroxide,  which,  after  washing,  is  dissolved  in  hydro- 
chloric or  sulphuric  acid. 

The  Element.*  A.  Preparation.  Elementary  zirconium 
may  be  obtained  in  the  amorphous  condition  (i)  by  reducing 
potassium  fluozirconate  with  potassium  (Berzelius),  and  (2) 
by  reducing  the  oxide  with  magnesium  (Phipson).  It  may 

*  Vid.  Zely  and  Hamburger,  Ztschr.  anorg.  Chem.  LXXXVH,  209. 


78  THE  RARER  ELEMENTS. 

be  obtained  in  crystalline  form  by  heating  potassium 
fluozirconate  with  aluminum  (Troost),  and  in  graphitic 
form1  by  heating  sodium  fluozirconate  with  iron  at 
850°  C. 

B.  Properties,  (i)  Zirconium  in  the  amorphous  con- 
dition is  a  black  powder.  Heated  in  the  air  it  burns  brightly 
to  the  oxide.  It  oxidizes  also  when  fused  with  alkali 
nitrates,  carbonates,  and  chlorates,  and  is  only  slightly 
attacked  by  acids. 

(2)  In  crystalline  form  zirconium  has  much  the  ap- 
pearance of  antimony.  Heated  in  the  air  it  oxidizes  very 
slowly.  It  is  not  acted  upon  by  fusion  with  alkali  nitrates, 
carbonates,  or  chlorates,  but  is  soluble  in  the  acids  upon 
the  application  of  heat.  The  density  of  the  pure  metal 
is  6.4;  its  melting-point  is  1530°  (Wedekind).* 

Compounds.  A.  Typical  forms.  The  following  are  typi- 
cal compounds  of  zirconium : 

Oxides,  ZrO2;  Zr2O3;  Zr2O5. 

Hydroxide,  Zr(OH)4. 

Chlorides,  ZrCl4;  also  double  salts  with  KC1  and  NaCl. 

Oxyhalides,  ZrOCl2+3H2O ;  ZrOBr2+3H2O ;  ZrI(OH)3+3H2O. 

Bromide,  ZrBr4. 

Iodide,   ZrI4. 

Fluoride,   ZrF4. 

Oxysulphide,  ZrOS. 

Sulphite,  Zr(S03)2. 

Sulphates,   Zr(S04)2  +  4H2O;  3Zr02-S03. 

Selenite,   Zr(SeO3)2. 

Nitrate,   Zr(NO3)4  +  5H2O. 

Phosphate,   Zr3(PO4)4. 

Pyrophosphate,   ZrP2O7. 

Carbonate,    3ZrO2-CO2  +  8H2O. 

Oxalates,   Zr(C2O4)2-2Zr(OH)4;  Zr(C2O4)2-K2C2O4.H2C2O4-H 

8H2O. 
Zirconates,  Na4ZrO4;  Li2ZrOs,  etc. 

*  U.  S.  Bureau  of  Standards  gives  ±1700°  C. 


ZIRCONIUM.  79 

Zirccnyl  *-nitric   or  nitrato-zirconic  acid,  H2ZrO(N03)4+ 

4H2O. 
Zirconyl-sulphuric  or  sulphatozirconic  acid,  H2ZrO(SC>4)2  + 

3H20. 

Fluozirconate,  K2ZrFe. 
Carbide,  ZrC. 
Silicide,  ZrSi. 
Hydride,  ZrH2. 
Nitride,  Zr2N3. 

B.  Characteristics.  In  chemical  structure  the  com- 
pounds of  zirconium  bear  a  strong  resemblance  to  those 
of  thorium,  titanium,  germanium,  and  silicon.  The  oxide, 
in  its  behavior  as  a  base  toward  oxides  having  more  acidic 
qualities,  resembles  the  oxide  of  thorium  (ThO2).  With 
the  weaker  acids,  carbonic  and  oxalic,  it  shows  weaker 
basic  properties  in  the  formation  of  basic  salts.  With 
strong  bases  it  manifests  acidic  properties,  like  the  oxide 
of  titanium,  and  forms  zirconates  (vid.  Typical  Forms, 
above).  The  chief  soluble  salts  are  the  nitrate  and  the 
sulphate.  The  hydroxide  of  zirconium  is  insoluble  in 
excess  of  the  alkali  hydroxides,  the  double  sulphate  with 
potassium  is  insoluble  in  a  solution  of  potassium  sulphate, 
and  the  oxalate  is  soluble  in  ammonium  oxalate.  Solutions 
of  pure  zirconium  salts  are  said  to  give  no  precipitate  with 
hydrofluoric  acid  or  potassium  hydronitride.  Turmeric 
paper,  when  dipped  into  a  solution  of  a  zirconium  salt  and 
dried,  is  colored  orange. 

Estimation.  Zirconium  is  usually  weighed  as  the  oxide 
(ZrO2)  obtained  by  ignition  of  the  hydroxide  or  oxalate. 

Separation.  Zirconium,  with  the  other  rare  earths,  may 
be  roughly  separated  from  other  elements  by  the  action 
of  oxalic  acid  (vid.  page  49).  For  the  separation  from 


*  Rosenheim,  Ber.  Dtsch.  chem.  Ges.  XL,  803.   810;   Hauser,  Zeitsch.  anorg. 
Chem.  Lm,  74;  LIV,  196. 


8o  THE  RARER  ELEMENTS.* 

yttrium,  cerium,  and  thorium  see  under  those  elements. 
The  separation  of  zirconium  from  iron  and  titanium  has 
received  a  good  deal  of  attention  from  chemists.  Some 
of  the  methods  that  have  been  suggested  follow. 

From  iron  zirconium  may  be  separated  (i)  by  the  action 
of  water  upon  an  ethereal  solution  of  the  chlorides, — the 
oxychloride  of  zirconium  being  precipitated  (Matthews, 
Jour.  Amer.  Chem.  Soc.  xx,  846) ;  (2)  by  the  action  of 
gaseous  hydrochloric  a'cid  and  chlorine  at  a  temperature  of 
about  200°  C.  upon  the  mixed  oxides, — the  ferric  chloride 
being  volatilized  (Havens  and  Way,  Amer.  Jour.  Sci.  [4] 
vm,  217);  (3)  by  treatment  with  phenylhydrazine, — the 
zirconium  being  precipitated  (Allen,  Jour.  Amer.  Chem. 
Soc.  xxv,  426) ;  (4)  by  the  action  of  sulphurous  acid 
on  neutral  solutions, — the  zirconium  being  precipitated 
(Baskerville,  Jour.  Amer.  Chem.  Soc.  xvi,  475). 

From  titanium  zirconium  may  be  separated  (i)  by 
boiling  a  solution  containing  the  two  elements  with  dilute 
sulphuric  and  acetic  acids, — titanic  acid  being  precipitated 
free  from  zirconium  (Streit  and  Franz,  J.  pr.  Chem.  cvm, 
75 ;  Zeitsch.  anal.  Chem.  ix,  388) ;  (2)  by  treating  solu- 
tions acid  with  sulphuric  or  hydrochloric  acid  with  zinc 
until  the  titanium  is  reduced  to  the  condition  of  the  sesqui- 
oxide,  and  then  adding  potassium  sulphate, — the  zirconium- 
potassium  sulphate  being  precipitated  (Pisani,  Compt. 
rend.  LVII,  298;  Chem.  News  x,  91,  218);  (3)  by  adding 
hydrogen  dioxide  and  sodium  phosphate  to  the  solution, — 
the  basic  phosphate  of  zirconium  being  precipitated  (Hille- 
brand,  Bull.  U.  S.  Geol.  Survey  No.  176,  75). 

EXPERIMENTAL  WORK  ON  ZIRCONIUM. 

Experiment  i .  Extraction  of  zirconium  salts  from  zircon. 
Fuse  5  grm.  of  finely  powdered  zircon  in  a  platinum  or 
nickel  crucible  with  about  15  grm.  of  acid  potassium 
fluoride.  Pulverize  the  fused  mass  and  extract  with  hot 


EXPERIMENTAL   WORK  ON  ZIRCONIUM.  81 

water  containing  a  few  drops  of  hydrofluoric  acid.*  Filter 
immediately  through  a  rubber  funnel  into  a  rubber  beaker. 
As  the  nitrate  cools,  potassium  fluozirconate  crystallizes 
out.  It  may  be  purified  by  recrystallization. 

Experiment  2.  Precipitation  of  zirconium  hydroxide, 
(Zr(OH)4).  (a)  To  a  solution  of  a  zirconium  salt  add  potas- 
sium, sodium,  or  ammonium  hydroxide.  Note  the  insolu- 
bility in  excess.  (6)  To  a  solution  containing  zirconium  add 
sodium  thiosulphate  in  solution  and  boil. 

Experiment  3.  Precipitation  of  zirconium  carbonate, 
(3ZrO2-CO2  +  8H2O).  (a)  To  a  solution  of  a  zirconium 
salt  add  sodium  or  potassium  carbonate.  Note  the  partial 
solubility  in  excess. 

(6)  Use  ammonium  carbonate  as  the  precipitant.  Note 
the  solvent  action  of  an  excess  and  the  precipitation  of 
the  hydroxide  on  boiling. 

(c)  Try  the  action  of  the  common  acids  upon  separate 
portions  of  zirconium  carbonate. 

Experiment  4.  Precipitation  of  zirconium  oxalate, 
(Zr(C2O4)2-2Zr(OH)4).  (a)  To  a  solution  of  a  zirconium 
salt  add  a  solution  of  oxalic  acid.  Note  the  effect  of  an 
excess  in  the  cold  and  on  warming. 

(6)  Use  ammonium  oxalate  as  the  precipitant.  Note 
the  solvent  action  of  an  excess  and  the  reprecipitation  by 
ammonium  hydroxide. 

Experiment  5.  Precipitation  of  zirconium  phosphate, 
(^ZrO2-^P2O5,  basic}.  To  a  solution  of  a  zirconium  salt 
add  sodium  phosphate.  Orthophosphoric  acid  precipi- 
tates the  normal  phosphate  (Zr3(PO4)4). 

Experiment  6.  Precipitation  of  zirconium  ferrocyanide, 
(ZrFeC6N6?).  To  a  solution  of  a  zirconium  salt  add  potas- 
sium ferrocyanide. 

Experiment  7.  Action  of  zirconium  salts  upon  turmeric 
paper.  Dip  a  piece  of  turmeric  paper  into  a  solution  of  a 

*  Glass  or  porcelain  dishes  must  not  be  us;d  when  hydrofluoric  acid  is  present. 


82  THE  RARER  ELEMENTS. 

zirconium  salt  acidified  with  hydrochloric  acid.  Dry  on  the 
side  of  a  test-tube  or  beaker,  as  in  testing  for  boric  acid. 
Note  the  yellowish-red  color. 

Experiment  8.  Precipitation  of  zirconium  peroxide 
(Zr2O5).  To  a  solution  of  a  zirconium  salt,  faintly  acidified, 
add  hydrogen  dioxide. 

Experiment  9.  Negative  tests  of  zirconium  salts.  Note 
that  neither,  hydrogen  sulphide  nor  potassium  fluoride  gives 
a  precipitate  with  zirconium  salts.  Ammonium  sulphide 
precipitates  the  hydroxide,  not  the  sulphide. 


CHAPTER  V. 
GALLIUM,*  Ga,  69.9. 

Discovery.  In  1875  Lecoq  de  Boisbaudran,  who  had 
done  much  work  with  spectrum  analysis,  notified  the 
Academic  des  Sciences  of  his  discovery  of  a  new  element 
in  a  zinc-blende  from  the  mine  of  Pierrefitte  in  the  Pyre- 
nees, and  proposed  for  it  the  name  Gallium  (Compt.  rend. 
LXXXI,  493;  Chem.  News  xxxn,  159).  The  individu- 
ality of  the  new  body  was  distinctly  indicated  by  the 
spectroscope,  but  so  small  was  the  amount  of  it  in  the 
possession  of  the  discoverer  that  few  of  its  reactions  were 
determined.  Among  the  properties  which  he  described, 
however,  were  the  following:  the  oxide,  or  perhaps  a  sub- 
salt,  was  thrown  down  by  metallic  zinc  in  a  solution  con- 
taining chlorides  and  sulphates;  in  a  mixture  containing 
an  excess  of  zinc  chloride  the  new  body  was  the  first  to 
be  precipitated  by  ammonia;  in  the  presence  of  zinc  it 
was  concentrated  in  the  first  sulphides  deposited;  the 
spark  spectrum  of  the  concentrated  chloride  showed  twc 
violet  lines,  one  of  them  of  considerable  brilliance. 

Occurrence.  Gallium  is  found  combined,  in  very  small 
amounts,  in  certain  minerals,  chiefly  zinc-blendes  from 
Bensberg  on  the  Rhine,  Pierrefitte,  and  other  localities. 
It  has  been  detected  in  some  American  zinc-blendes  (Chem. 
Ztg.  (1880),  443).  The  Bensberg  sphalerite,  one  of  the 
richest  sources,  contains  0.016  grm.  per  kilo.  It  has  been 
found  also  in  commercial  aluminum  and  iron  (Boulanger 
and  Bardet,  Compt.  rend.  CLVII,  718;  Ramage,  Chem.  News 
cvin,  280). 

Hartley  and  Ramage  obtained  the  following  interesting 
results  by  means  of  the  spectroscope  (Jour.  London  Chem. 

*  The  discovery  of  gallium  was  predicted  by  Mendeleeff  in  1869,  and  the 
hypothetical  element  was  named  Ekaluminum.  It  was  given  the  atomic  weight 
of  68,  and  the  specific  gravity  of  6. 

83 


84  THE  RARER  ELEMENTS. 

Soc.  (1897),  533,  547):  the  presence  of  gallium  was  indicated 
in  thirty-five  out  of  ninety-one  iron  ores  examined;  in  all 
the  magnetites,  seven  in  number;  in  all  the  aluminum 
ores,  fifteen  in  number,  mostly  kaolin  and  bauxite;  in 
four  out  of  twelve  manganese  ores;  and  in  twelve  out  of 
fourteen  zinc-blendes. 

In  1915  McCutcheon  noticed  some  mercury-like  globules 
upon  the  surface  of  a  leady  residue  from  the  distillation  of 
zinc.  Since  the  residue  had  been  stored  away  in  a  warm 
place,  the  observer  decided  to  subject  it  to  the  action  of  moist 
steam.  This  treatment  resulted  in  a  more  abundant  sepa- 
ration of  the  peculiar  material,  which,  from  the  character 
of  its  source  and  its  low  melting-point,  suggested  the  element 
gallium.  It  proved  to  be  essentially  an  alloy  of  that  element 
with  indium.*  Rough  analyses  of  these  products  showed 
the  gallium-indium  alloy  to  contain  about  10  per  cent,  of 
indium,  with  small  amounts  of  zinc  and  lead,  and  spectro- 
scopic  traces  of  copper  and  silver.  The  leady  residue  con- 
tained about  3  per  cent,  of  gallium  and  indium  together. 
It  also  gave  spectroscopic  evidence  of  the  presence  of  ger- 
manium, f 

Extraction,  (a)  Salts  of  gallium  are  obtained  by  the  fol- 
lowing process :  The  mineral  is  dissolved  in  aqua  regia  and 
the  excess  of  acid  expelled  by  boiling.  When  the  solution  is 
cold,  pure  zinc  is  added,  which  precipitates  the  antimony, 
arsenic,  bismuth,  copper,  cadmium,  gold,  lead,  mercury, 
silver,  tin,  selenium,  tellurium,  and  indium.  These  are 
filtered  off  while  there  is  still  some  evolution  of  hydrogen, 
and  the  filtrate  is  boiled  from  six  to  twenty-four  hours 
with  metallic  zinc.  Gallium  is  precipitated  as  a  basic 
salt,  together  with  salts  of  aluminum,  iron,  zinc,  etc.  To 
obtain  the  gallium  salt  in  a  more  nearly  pure  condition 

*  Hillebrand  and  Scherrer,  J.  Ind.  Eng.  Chem.  vm,  225;  Browning  and  Uhler, 
Amer.  Jour.  Sci.  XLI,  351. 

t  The  spectroscopic  examination  was  made  by  Dr.  H.  S.  Uhler  of  Yale  Uni- 
versity. 


GALLIUM.  %4a 

the  precipitate  is  dissolved  in  hydrochloric  acid,  the  solu- 
tion is  treated  with  hydrogen  sulphide,  and  after  nitra- 
tion and  the  removal  of  the  excess  of  hydrogen  sulphide 
by  boiling,  sodium  carbonate  is  added  in  small  portions, , 
The  gallium  salt  is  the  first  to  be  precipitated,  and  the  pre- 
cipitates are  collected  as  long  as  they  show  the  gallium, 
lines  in  the  spark  spectrum.*  These  precipitates  are  dis- 
solved in  sulphuric  acid  and  the  solution  is  diluted  largely 
with  water  and  boiled.  The  basic  sulphate  of  gallium 
which  is  thus  thrown  down  is  dissolved  in  sulphuric  acid, 
and  potassium  hydroxide  is  added  in  excess.  Iron  if 
present  is  removed  at  this  point  by  nitration  and  the 
gallium  oxide  is  then  precipitated  from  the  nitrate  by 
carbon  dioxide.  The  discoverer  prepared  62  grams  of 
the  element  from  2400  kilograms  of  blende,  (b)  Gallium 
may  be  obtained  from  the  leady  residue  from  the  puri- 
fication of  zinc  (vid.  Experiment  i). 

The  Element.  A.  Preparation.  Gallium  in  the  ele- 
mentary condition  has  been  obtained  by  subjecting  an 
alkaline  solution  of  the  oxide  to  electrolysis. 

B.  Properties.  A  gray,  lustrous  metal,  showing  green- 
ish-blue lights  on  reflecting  surfaces,  gallium  is  malleable 
and  fairly  hard.  Its  fusing-point,  30.15°  C.,  is  so  low 
that  it  melts  readily  from  the  warmth  of  the  hand.  In 
water,  and  in  air  at  ordinary  temperatures,  it  is  unchanged ; 
when  heated  in  air  or  oxygen  it  is  oxidized  only  superfi- 
cially; in  fact,  it  may  be  heated  to  redness  over  a  Bunsen 
burner  without  appreciable  change  in  weight.  It.  combines 
rapidly  with  chlorine,  more  slowly  with  bromine,  and  not 
at  all  with  iodine  unless  heat  is  applied.  Gallium  is  soluble 
in  hydrochloric  and  warm  nitric  acids,  and  somewhat 
soluble  in  potash  and  ammonia  solutions.  It  alloys  easily 
with  aluminum,  and  these  alloys  decompose  cold  water 
rapidly.  Its  specific  gravity  is  5.88. 

*  Two  violet  lines,  4172  and  4033. 


846  THE  RARER  ELEMENTS. 

Compounds.  A.  Typical  forms.  The  following  com- 
pounds of  gallium  are  known: 

Oxides GaO?  Ga2O3 

Hydroxide -  Ga(OH)3? 

Chlorides GaCl2  GaCl3 

Bromide GaBr3 

Iodide GaI3 

Nitrate Ga2(NO3)6 

Sulphate Ga2(SO4)3 

Double  sulphate  (alum)  Ga2(SO4)3 •  (NH4)2SO4*  +  24H2O 

Ferrocyanide Ga4(FeC6N6)3. 

B.  Characteristics.  The  compounds  of  gallium  resem- 
ble those  of  aluminum  in  forming  alums  and  in  having  a 
hydroxide  soluble  in  excess  of  sodium  or  potassium  hy- 
droxide. The  salts  are  colorless  and  soluble,  and  in  dilute 
solutions  tend,  on  being  heated,  to  become  basic  and  sepa- 
rate from  the  solution.  The  oxide-  (Ga2O3)  is  insoluble  in 
acids  and  alkalies  after  ignition.  Gallium  also  resembles 
indium  in  forming  alums,  but  differs  from  that  element  in 
that  its  hydroxide  is  soluble  in  potassium  and  sodium 
hydroxides.  Its  alums  are  less  soluble  in  water  than  those 
of  indium.  A  very  characteristic  reaction  for  gallium  is  the 
formation  of  the  ferrocyanide  in  fairly  strong  hydrochloric 
acid.  This  reaction  is  useful  in  separating  it  from  aluminum,  f 

Estimation.  Gallium  is  usually  weighed  as  the  oxide  (Ga2O3). 

Separation.!     Vid.  Extraction. 

INDIUM,  In.  114.8. 

Discovery.  Indium  was  discovered  by  Reich  and 
Richter  in  1863,  in  the  course  of  an  examination  of  two 

*  The  caesium  alum  forms  more  readily  than  the  ammonium  alum,  and  seems 
well  adapted  for  the  separation  from  indium  by  fractional  crystallization,  and  for 
the  micro-chemical  detection. 

t  Aluminum  may  be  separated  from  gallium  by  saturating  a  solution  of  the 
chlorides  with  HC1  gas.  Aids  is  precipitated  (Browning  and  Porter,  Amer.  Jour. 
Sci.  XLIV,  221). 

t  For  a  detailed  study  of  the  separation  of  gallium,  see  many  articles  by  Lecoq 
de  Boisbaudran,  Compt.  rend,  xciv-xcvm. 


INDIUM.  gs 

ores  consisting  mainly  of  the  sulphides  of  arsenic,  zinc, 
and  lead  (J.  pr.  Chem.  LXXXIX,  441).  These  ores  had  been 
freed  from  the  greater  part  of  their  arsenic  and  sulphur 
by  roasting,  and  the  residue  had  been  evaporated  to  dry- 
ness  with  hydrochloric  acid  and  distilled.  The  crude 
chloride  of  zinc  thus  obtained  was  examined  with  the 
spectroscope  for  thallium,  since  the  presence  of  that  element 
had  been  indicated  in  similar  ores  from  the  Freiberg  mines. 
Instead  of  the  thallium  line,  however,  appeared  one  of 
indigo  blue  never  before  observed.  The  color  suggested 
the  name  Indium  for  the  unknown  element  present. 

Occurrence.  Indium  occurs  in  very  small  amounts, 
combined  with  sulphur,  in  many  zinc-blendes.  It  has  been 
found  in  zinc-blende  from  Freiberg  and  Breitenbrun  in 
Saxony,  and  from  Schonfeld  in  Bohemia,  in  christophite,  a 
variety  of  zinc-blende;  in  zinc  prepared  from  these  ores; 
and  in  the  flue-dust  from  ovens  used  for  roasting  zinc  ores. 
It  has  also  been  found  in  wolframite  from  Zinnwald.  The 
proportion  of  indium  in  the  minerals  named  varies  from 
one  tenth  of  one  per  cent,  to  mere  traces.  Lockyer  de- 
tected it  in  the  atmosphere  of  the  sun.  Hartley  and  Ra- 
mage  (Jour.  London  Chem.  Soc.  (1897).  533,  547)  have  dis- 
covered it  spectroscopically  in  many  iron  ores, --notably 
siderites, — in  some  manganese  ores,  in  zinc-blendes,  in 
five  tin  ores  examined,  and  in  many  pyrites.* 

Extraction.  Indium  salts  may  be  obtained  as  follows 
from  zinc  that  has  been  extracted  from  indium-bearing 
blendes.  The  crude  metal  is  nearly  dissolved  in  hydro- 
chloric or  nitric  acid,  and  the  solution  is  allowed  to  stand 
twenty-four  hours  with  the  undissolved  metal.  A  spongy 
mass,  consisting  of  the  indium  together  with  lead,  copper, 
cadmium,  tin,  arsenic,  and  iron,  collects  upon  the  residual 
zinc.  This  mass  is  washed  with  water  containing  some 

*  For  further  discussion  of  the  wide  distribution  of  this  element  vid.  Wernadski, 
Bull.  Acad.  St.  Petersburg  (1911),  187  and  1007;  Urbain,  Compt.  rend.  CXLIX, 
602;  Hillebrand  and  Scherrer,  J.  Ind.  Eng.  Chem.  vm,  225. 


86  THE  RARER   ELEMENTS, 

sulphuric  acid ;  it  is  then  dissolved  in  nitric  acid  and  evapo- 
rated with  sulphuric  acid  until  all  the  nitric  acid  is  removed. 
By  this  process  the  lead  is  precipitated,  and  it  may  be 
removed  by  filtration.  The  solution  that  remains  is  treated 
with  ammonium  hydroxide  in  excess,  and  the  hydroxides 
of  iron  and  indium  are  filtered  off  and  dissolved  in  a  small 
amount  of  hydrochloric  acid.  This  solution  is  treated 
with  an  excess  of  acid  sodium  sulphite  and  boiled.  In- 
dium is  precipitated  as  the  basic  sulphite  (In2(SO3)3  •  In2('OH)a 
+  5H2O).  Indium  may  also  be  separated  from  iron  by 
treating  the  chlorides  with  potassium  sulphocyanicb  and 
extracting  the  ferric  sulphocyanide  with  ether,  Agaln.it 
may  be  separated  -from  aluminum  and  iron  by  treating 
the  chlorides  in  alcoholic  solution  with  pyridine.  The 
indium  is  precipitated  as  a  compound  of  indium  chloride 
and  pyridine  (InCl3-3C5H5N)  (Dennis,  Ber.  Dtsch.  chem. 
Ges.  xxxvn,  961 ;  Renz,  ibid,  xxxvn,  2110;  Mathers,  Jour. 
Amer.  Chem.  Soc.  xxx,  209.  Vid.  also  Experiment  i). 

The  Element.  A.  Preparation.  Elementary  indium 
may  be  obtained  (i)  by  heating  the  oxide  with  carbon  cr 
in  a  current  of  hydrogen;  (2)  by  heating  the  oxide  with 
sodium  under  a  layer  of  dry  sodium  chloride;  (3)  by  treat- 
ing the  salts  with  zinc;  (4)  by  electrolyzing  the  sulphate 
in  the  presence  of  formic  acid  (Dennis). 

B.  Properties.  Indium  is  a  soft  white  metal,  less  vola-, 
tile  than  cadmium  and  zinc.  It  melts  at  155°  C.  (Thiel). 
At  ordinary  temperatures  it  is  stable  in  the  air,  but  when 
heated  it  ignites  and  burns  with  a  violet  flame  to  the 
oxide.  It  does  not  decompose  boiling  water.  It  dissolves 
easily  in  hydrochloric,  nitric,  and  sulphuric  acids.  It 
forms  alloys  with  lead  and  thallium.  Its  specific  gravity 
is  given  at  from  7.1  to  7.4. 

Compounds.*  A.  Typical  forms.  The  following  com- 
pounds of  indium  are  known : 

*  The  following  references  will  be  found  helpful :   Thiel,  Ztsch.  anorg.  Chem. 
XL,  280;  LXVI,  288;  Mathers,  Jour.  Amer.  Chem.  Soc.  xxix,  485;  xxx,  86,  211. 


INDIUM.  87 

Oxides InO ;  In203 

Hydroxide In(O  H)3 

Fluoride InF3  +  3H2O 

Chlorides .InCl;  InCl2 ;  InCl3 

Oxychloride InOCl 

Indium  -  hydrochloric 

acid H3InCla 

Bromide InBr3 

Iodide InI3 

Nitrate In2(NO8)6  +  9H2O 

Sulphate In2(SOJ3 

Double  sulphates ....  In2(SO4)3  •  K2SO4  +  24H2O ; 

In2(S04)3-(NH4)3S04  + 
24H2O 

Sulphite In2(S03)8-In2(OH)6  +  sH20 

Sulphides In2S;  InS;    In2S3 

Sulpho  salts K2In2S4 ;  Xa2In.,S4 

B.  Characteristics.  Indium  resembles  aluminum,  iron, 
and  gallium  in  forming  alums,  but  these  alums  seem  to  re- 
semble those  of  iron  more  than  those  of  the  other  elements. 
It  resembles  zinc  in  forming  a  sulphide  with  hydrogen  sul- 
phide, but  in  the  case  of  indium  this  salt  is  yellow.  The 
hydroxide  is  insoluble  in  both  sodium  and  potassium  hy- 
droxides, as  well  as  in  ammonium  hydroxide.  Indium 
monoxide  is  a  dark  powder  slowly  soluble  in  dilute  acids. 
The  sesquioxide  is  a  yellowish-white  powder  easily  soluble  in 
warm  acid  and  more  infusible  than  aluminum  oxide.  The 
dichloride  is  formed  directly  by  the  union  of  chlorine  with  'the 
metal,  and  is  a  white,  crystalline  mass ;  in  water  it  separates 
into  the  trichloride  and  the  metal.  By  fusion  of  the  di- 
chloride with  elementary  indium  the  monochloride  is  formed, 
—  a  reddish-black,  crystalline  substance.  The  trichloride 
is  formed  also  by  the  action  of  chlorine  in  excess  upon 
the  metal;  it  is  white  like  the  dichloride  and  dissolves  in 
water  with  the  evolution  of  heat.  The  nitrate  and  the  sul- 
phate are  readily  soluble  in  water  and  tend  to  form  basic 


88  THE  RARER  ELEMENTS. 

salts  on  being  heated.  Solutions  of  indium  salts  color  the 
flame  violet  and  give  a  characteristic  flame  spectrum. 

Estimation.  Indium  is  generally  determined  as  the 
oxide  (In2O3),  obtained  by  ignition  of  the  hydroxide,  or  as 
the  sulphide  (111283),  obtained  by  precipitation  with  hydro- 
gen sulphide  in  the  presence  of  sodium  acetate. 

Separation.  The  separation  of  this  very  rare  element 
from  those  elements  with  which  it  is  usually  associated  is 
treated  under  extraction. 

EXPERIMENTAL  WORK   ON   GALLIUM  AND 
INDIUM. 

Experiment  i.  Extraction  of  indium  and  gallium  from 
the  leady  residue  from  purification  of  zinc  (approximate  com- 
position, Pb  95.6%,  In  and  Ga  3%,  Zn  1.2%,  Cu  traces). 

Dissolve  the  sample  in  a  small  amount  of  a  mixture  of 
strong  nitric  acid  and  water  in  equal  parts,  warming  to 
aid  solution.  Evaporate  to  dryness,  finishing  the  evapora- 
tion on  a  steam  bath.  Treat  the  dry  residue  with  enough 
sulphuric  acid  (i-i)  to  precipitate  lead  sulphate  completely; 
warm,  filter,  and  wash  with  a  little  sulphuric  acid  (1-3). 
To  the  filtrate  add  ammonium  chloride  and  ammonium 
hydroxide  to  alkalinity,  and  boil.  Filter  off  indium  hy- 
droxide and  gallium  hydroxide  and  wash.  Dissolve  this 
precipitate  in  a  small  amount  of  hydrochloric  acid,  evapo- 
rate to  a  few  cubic  centimeters,  and  test  in  the  flame  and 
before  the  spectroscope  for  indium.  To  separate  gallium 
treat  this  solution  with  a  slight  excess  of  sodium  hydroxide 
and  warm.  Wash  the  residue,  dissolve  in  hydrochloric  acid 
and  test  again  for  indium.  To  the  filtrate  add  hydro- 
chloric acid  to  acidity  and  potassium  ferrocyanide.  Gallium 
ferrocyanide  is  precipitated. 

Experiment  2 .    Formation  of  indium  hydroxide  (In (OH)  3) . 

(a)  To  a  drop  of  a  solution  of  an  indium  .salt  add  ammo- 
nium chloride  and  a  mmonium  hydroxide  and  boil.  Note  the 
precipitate  of  indium  hydroxide  and  its  insolubility  in  excess. 


THALLIUM.  89 

(b)  To  another  portion  add  sodium  hydroxide.  Note 
here  also  the  insolubility  in  excess. 

Experiment  3.  Formation  of  gallium  hydroxide  (Ga(OH)s). 
Repeat  the  foregoing  procedure,  using  a  drop  of  a  solution 
of  a  gallium  salt  instead  of  the  indium.  Compare  the 
solubility  of  gallium  hydroxide  with  that  of  indium  hydroxide 
in  excess  of  the  reagents  used. 

Experiment  4.  Formation  of  indium  basic  sulphite 
(In(OH)SO3,  typical).  To  a  few  drops  of  a  solution  of  an 
indium  salt  add  a  few  drops  of  a  solution  of  acid  ammonium 
sulphite,  and  boil. 

Experiment  5.  Formation  of  gallium  ferrocyanide 
(Ga4(FeC6N6)3.  Try  the  action  of  potassium  ferrocyanide 
on  an  acidified  solution  of  a  gallium  salt.  Note  precipitate. 

Experiment  6.  Spectroscopic  test  for  indium.  Test  a 
solution  of  an  indium  salt  in  the  flame,  before  the  spectro- 
scope. 

THALLIUM,  Tl,  204. 

Discovery.  Some  years  previous  to  1861  Crookes  had 
been  engaged  in  the  extraction  of  selenium  from  a  selen- 
iferous  deposit  which  he  had  obtained  from  the  sulphuric- 
acid  manufactory  at  Tilkerode  in  the  Hartz  Mountains. 
Some  residues,  left  after  the  purification  of  the  selenium, 
and  supposed  to  contain  tellurium,  were  set  aside  and 
not  examined  until  1861,  when,  needing  tellurium,  Crookes 
vainly  tried  to  isolate  it  by  various  chemical  methods. 
At  length  he  resorted  to  spectrum  analysis  and  tested 
some  of  the  residue  in  the  flame.  The  spectrum  of  selen- 
ium appeared,  and  as  it  was  fading,  and  he  was  looking  for 
evidence  of  tellurium,  a  new  bright-green  line  flashed  into 
view.  The  element  whose  presence  was  thus  indicated 
received  the  name  Thallium,  from  the  Greek  Bahkos,  or 
the  Latin  thallus,  a  budding  twig  (Chem.  News  in,  194). 

About  the  same  time  Lamy  announced  the  discovery 
of  the  same  element  (Ann.  Chim.  Phys.  [3]  LXVII,  385), 


9o  THE  RARER  ELEMENTS. 

but  after  much  discussion  and  the  presentation  of  much 
evidence  on  both  sides  it  was  declared  that  Crookes  had 
the  priority  of  discovery. 

Occurrence.  Thallium  occurs  in  certain  very  rare 
minerals : 

Crookesite,  (Cu,Tl,Ag)2Se,  contains  16-19%  Tl 
Lorandite,  TlAsS2,  5  9-60%  Tl 

Hutchinsonite,  (Tl,Ag,Cu)2S-As2S3+PbS-As2S3,  contains 

18-25%  Tl 
Vrbaite,  (TlAs2SbS5),  contains  29-30%  Tl. 

It  is  found  also  in  very  small  quantities  in  berzelianite, 
(Cu2Se) ;  in  some  zinc-blendes  and  copper  pyrites ;  in  iron 
pyrites  from  Theux,  Namur,  Philippe ville,  Alais,  and  Nantes  ; 
in  lepidolite  from  Mahren;  and  in  mica  from  Zinnwald. 
It  has  been  detected,  together  with  cesium,  rubidium,  and 
potassium,  in  the  mineral  waters  of  Nauheim  and  Orb. 
Its  presence  in  the  flue -dust  from  some  iron  furnaces  and 
sulphuric-acid  works,  as  well  as  in  some  crude  sulphuric 
and  hydrochloric  acids,  may  be  traced  to  its  presence  in 
the  pyrites  used.  It  has  been  found  in  commercial 
platinum. 

Extraction.  Thallium  salts  may  be  extracted  by  the 
following  methods: 

(1)  From  minerals.  The  finely  powdered  mineral  is  dis- 
solved in  aqua  regia.     The   solution  is  evaporated  with 
sulphuric  acid  until  the  free  acid  has  been  removed ;  it  is 
then    diluted    abundantly    with    wrater,    neutralized    with 
sodium  carbonate,    and  treated  with  potassium  cyanide 
in  excess.     This  precipitates  the  bismuth  and  lead,  which 
are   filtered   off.     The   filtrate   is   treated   with   hydrogen 
sulphide,  which  precipitates  the  cadmium,  mercury,  and 
thallium   as   the    sulphides.     Very    dilute    sulphuric    acid 
dissolves  the  thallium  sulphide,  leaving  the  cadmium  and 
mercury  sulphides  undissolved  (Crookes). 

(2)  From  flue-dust.      The  material  is  treated  with  an 


THALLIUM.  gI 

equal  weight  of  boiling  water  in  a  large  wooden  tub,  and  is 
allowed  to  stand  twenty-four  hours.  The  liquid  in  si- 
phoned off  and  is  precipitated  with  hydrochloric  acid.* 
The  crude  chloride  thus  obtained  is  treated  with  an  equal 
weight  of  sulphuric  acid,  and  heated  to  expel  the  hydro- 
chloric acid  and  the  greater  part  of  the  excess  of  sulphuric. 
The  sulphate  obtained  is  dissolved  in  water,  the  solution 
is  neutralized  with  chalk  and  filtered.  By  the  addition 
of  hydrochloric  acid  to  the  filtrate,  nearly  pure  thallous 
chloride  is  precipitated  (Chem.  News  vm,  159). 

The  Element.  A.  Preparation.  The  element  thallium 
may  be  obtained  ( i )  by  fusing  a  mixture  of  thallous  chloride 
and  sodium  carbonate  with  potassium  cyanide;  (2)  by 
submitting  the  carbonate  or  the  sulphate  to  electrolysis; 
(3)  by  heating  the  oxalate;  and  (4)  by  precipitating  with 
zinc  from  an  alkaline  solution  of  a  thallous  salt. 

B.  Properties.  Metallic  thallium  is  in  color  whitish 
to  blue  gray,  with  the  luster  of  lead.  It  is  soft  and  malle- 
able and  melts  at  302°  C.  It  forms  alloys  with  many  of 
the  metals  (Kurnakow,  Zeitsch.  anorg,  Chem.  xxx,  86;  LIT, 
430;  Baar,  ibid.  LXX,  352).  It  •  oxidizes  readily  at  high 
temperatures,  but  is  not  acted  upon  by  water  free  from  air. 
It  is  soluble  in  dilute  nitric  and  sulphuric  acids.  It  is  a 
poor  Conductor  of  electricity.  The  specific  gravity  of 
thallium  is  u.88. 

Compounds.!  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  thallium: 

Oxides TljO  T12O3 

Hydroxides T1OH  Tl(OH), 

•Carbonate T12CO3 

*  Three  tons  of  dust  gave  sixty-eight  pounds  of  crude  thallous  chloride. 

t  See  also  Hawley,  Jour.  Amer.  Chem.  Soc.  xxix,  300,  ion;  Stortenbeker; 
Rec.  trav.  chim.  Pays-Bas,  xxvi,  248;  Thomas,  Ann.  chim.  phys.  xi,  [8],  204; 
Franklin,  Jour.  Amer.  Chem.  Soc.  xxxvn,  2279;  Ball,  J.  Chem.  Soc.  (London) 
•cm,  2110,  2130;  Buchtala,  J.  prakt.  Chem.  [2]  Lxxxvm,  771;  Beurath,  Ztschr. 
anorg.  Chem.  xcm,  161. 


92  THE  RARER  ELEMENTS. 

Chlorides T1C1  T1C13+H2O 

Double  chlorides  . .  T1C1  •  HgCl2 ;  3T1C1  •  FeCU ;          T1CU  •  3KC1+ 2H2O ; 

TICl-AuCU;  etc.*  etc. 

Chlorate T1C1O3 

Perchlorate T1C1O4 

Bromides TIBr  TlBrs 

Double  bromides. .  TlBr3-  KBr+  2H2O; 

TlBr3.3TlBr 

Bromate TIBrO, 

Iodides Til  Til, 

Double  iodides ....  Til  •  KI  Til,  •  NH4I 

lodates T1IO,  T1(IO3)3 

Periodate 3T12O3  •  I2O74-  3oH2O 

Thiosulphate T12S2O, 

Sulphides T12S  T12SS 

Sulphite T12SO3 

Sulphates T12SO4;  T1HSO4  Tl^SOJ, 

Double  sulphates . .  with  MgSO4)  ZnSO4,  CuSO4,  etc. 

Alums T12S04-  A12(S04)3+  24H2O; 

Tl2S04-Fe2(S04)3+24H20 

Nitrates T1NO3  T1(NO3)3+  4H2O 

Phosphates T13PO4;  T14PZO7;  T1PO,  T1PO4+  2H2O 

Arseniates TlsAsO4  TlAsO4+  2H2O 

Cyanides T1CN  T1(CN)3  -  T1CN 

Sulphocyanide T1SCN 

Ferrocyanide Tl4Fe(CN),4-  2HjO 

Silicofluoride Tl2SiF, 

Chromates Tl2CrO4 ;  Tl2Cr2O, 

Chloroplatinate  . . .  Tl,PtCl, 

Molybdate Tl2MoO4 

Tungstate T12\VO4 

Vanadates T13VO4;  T14V2O7;  T1VO3 

B.  Characteristics.  Thallium  compounds  are  known 
in  two  conditions  of  oxidation,  the  thallous,  (TLO),  and 
the  thallic,  (T12O3) .  The  lower  condition  is  the  more  stable ; 
consequently  the  thallous  compounds  are  the  more  numer- 
ous and  the  better  known.  When  the  metal  is  allowed 
to  oxidize  in  the  air  it  forms  the  thallous  oxide,  but  when  it 
is  melted  in  an  atmosphere  of  oxygen,  thallic  oxide  is  ob- 
tained. Thallic  chloride,  bromide,  and  iodide  may  be 
formed  by  treating  the  corresponding  thallous  salts  with 

*  Vid.  also  Korreng,  Chem.  Zentr.  (1914)  i,  610. 


THALLIUM. 


93 


an  excess  of  chlorine,  bromine,  and  iodine,  respectively. 
In  general,  the  thallous  salts  may  be  oxidized  to  the  thallic 
form  by  strong  oxidizing  agents,  such  as  potassium  per- 
manganate, lead  dioxide,  barium  dioxide,  etc.  Thallium 
in  the  lower  condition  resembles  the  alkalies  potassium, 
caesium,  and  rubidium  in  having  a  soluble  hydroxide,  car- 
bonate, and  sulphate,  and  an  insoluble  chloroplatinate  and 
cobaltic  nitrite;  also  in  forming  alums.  It  resembles  lead 
in  forming  an  insoluble  sulphide  and  chromate,  and  in 
having  halogen  salts  difficultly  soluble  in  cold  water  but 
readily  soluble  in  hot  water.  The  thallous  salts  are  color- 
less when  the  base  is  combined  with  a  colorless  acid.  The 
sulphide  is  brownish  black.  The  thallic  salts  are  in  gen- 
eral unstable,  and  on  being  heated  with  water  tend  to 
precipitate  the  oxide  (T12O3-H2O).  They  may  be  easily 
reduced  to  the  lower  condition  by  the  action  of  reducing 
agents.  They  may  be  formed  by  the  careful  treatment 
of  thallic  oxide  with  acids  as  well  as  by  the  action  of  strong 
oxidizing  agents  upon  the  thallous  salts.  Thallic  hydroxide 
is  insoluble,  and  resembles  ferric  hydroxide  in  color.  The 
halogen  salts,  the  nitrate  and  the  sulphate  of  thallium  in 
the  thallic  condition  are  soluble.  Solutions  of  thallium 
salts  in  either  condition  of  oxidation  give  to  the  flame  a 
characteristic  green  color. 

Estimation.*  A.  Gravimetric.  Thallium  is  generally 
weighed  in  the  thallous  condition  (i)  as  the  chloroplati- 
nate, (Tl2PtCl6),  after  precipitation  by  chloroplatinic  acid 
(Crookes,  Select  Methods,  Second  Edition,  380) ;  (2)  as  the 
iodide  (Til),  after  precipitation  by  potassium  iodide 
(Werther,  Zeitsch.  anal.  Chem.  in,  i,  and  T.  B.  (1864),  712; 
Long,  Zeitsch.  anal.  Chem.  xxx,  342) ;  (3)  as  the  chro- 

*See  also  Hebberling,  Liebig  Annal.  cxxxv,  207;  Phipson,  Compt.  rend, 
xxvra,  563;  Neumann,  Liebig  Annal.  CCXLIV,  349;  Feit,  Zeitsch.  anal.  Chem. 
xxvirr,  314;  Carnot,  Compt.  rend,  cix,  177;  Sponholz,  Zeitsch.  anal.  Chem. 
xxxi,  519;  Thomas,  Compt.  rend,  cxxx,  1316;  Marshall,  Jour.  Soc.  Chem.  Ind. 
xix,  99^ 


94  THE  RARER  ELEMENTS. 

mate  (Tl2Cr04),  after  precipitation  in  alkaline  solution  by 
potassium  chromate  (Browning  and  Hutchins,  Amer. 
Jour.  Sci.  [4]  vin,  460);  (4)  as  the  sulphate  (T12SO4),  after 
evaporation  of  appropriate  salts  with  sulphuric  acid  in  ex- 
cess and  ignition  at  low  red  heat,  or  as  the  acid  sulphate, 
(TlHSCh),  obtained  by  substituting  for  ignition  heating  at 
220°-24o°  C.  (Browning,  Amer.  Jour.  Sci.  [4]  ix,  137).  It 
may  be  estimated  also  by  weighing  the  gold  precipitated 
according  to  the  equation:  3TiU-i-2AuBr3  =  2Au  +  3TlClBr? 
(Thomas,  Ann.  chim.  phys.  xi  [8],  204). 

B.  Volumetric.  Thallium  is  estimated  volumetric- 
ally  (i)  by  the  oxidation  of  thallous  salts  with  perman- 
ganate (Crookes,  Select  Methods,  Second  Edition,  381) ; 
(2)  by  the  action  of  potassium  iodide  upon  thallic  salts, 
as  shown  in  the  following  equation  (Thomas,  Compt.  rend, 
cxxxiv,  655):  T1C13  +  3KI=T1I  +  3KC13  +  I2. 

Separation.*  In  the  more  stable  thallous  condition,  to 
which  thallic  salts  may  readily  be  reduced,  thallium  may 
be  separated  as  follows:  from  the  metals  which  give 
precipitates  with  hydrogen  sulphide  in  acid  (but  not  acetic) 
solution,  by  hydrogen  sulphide;  from  elements  which 
form  insoluble  hydroxides  with  the  alkali  hydroxides,  by 
these  reagents;  and  from  the  alkalies  and  alkali  earths, 
by  ammonium  sulphide. 


EXPERIMENTAL  WORK  ON  THALLIUM. 

Experiment  i.  Extraction  of  thallium  salts  from  flue- 
dust.  The  method  described  under  Extraction  may  be 
followed. 

Experiment  2.  Precipitation  of  thallous  chloride,  bro- 
mide, and  iodide  (T1C1;  TIBr;  Til),  (a)  To  a  solution  of 
a  thallous  salt  add  hydrochloric  acid  or  a  chloride  in  solu- 

*  See  Crookes,  Select  Methods,  Second  Edition,  382-386. 


EXPERIMENTAL  WORK  ON  THALLIUM.  95 

tion.  Note  the  solvent  action  of  boiling  water.  Try 
the  effect,  of  cooling  the  hot  solution. 

(6)  Repeat  the  experiment,  using  potassium  bromide 
as  the  precipitant. 

(c)  Try  similarly  potassium  iodide. 

Experiment  3.  Precipitation  of  thallium  chloroplatinate 
(Tl2PtCl6).  To  a  solution  of  a  thallous  salt  add  a  few 
drops  of  a  solution  of  chloroplatinic  acid. 

Experiment  4.  Precipitation  of  thallium  cobaltic  nitrite. 
To  a  solution  of  a  thallous  salt  add  a  few  drops  of  a  solu- 
tion of  sodium  cobaltic  nitrite. 

Experiment  5.  Precipitation  of  thallous  chromate 
(Tl2CrO4).  To  a  solution  of  a  thallous  salt  add  some  potas- 
sium chromate  in  solution.  Try  the  action  of  acids  upon 
the  precipitate. 

Experiment  6.  Precipitation  of  thallous  sulphide  (T1,S). 
(a)  Through  a  solution  of  a  thallous  salt  acidified  with 
dilute  sulphuric  acid  pass  hydrogen  sulphide.  Note  the 
absence  of  precipitation.  Divide  the  solution,  and  to  one 
part  add  ammonium  acetate  and  to  the  other  ammonium 
hydroxide. 

(6)  Try  the  action  of  ammonium  sulphide  upon  a  thal- 
lous salt  in  solution. 

Experiment  7.  Oxidation  of  thallous  salts.  (a)  To 
a  solution  of  a  thallous  salt  acidified  with  sulphuric 
acid  add  gradually  a  little  potassium  permanganate. 
Note  the  disappearance  of  the  color  of  the  perman- 
ganate. 

(6)  To  a  solution  of  a  thallous  salt  add  bromine 
water  until  the  color  of  the  bromine  ceases  to  fade. 
To  one  portion  add  a  few  drops  of  a  soluticn  of  a 
chioride  or  bromide.  Note  the  absence  of  precipitation. 
To  another  portion  add  sodium  or  potassium  hydroxide. 
Note  the  precipitation  of  brown  thallic  hydroxide, 
(T1203-H20). 

Experiment    8.     Reduction  of  a  thallic  salt.     To  a  solution 


-p6  THE  RARER  ELEMENTS. 

of  a  thallic  salt  formed,  for  example,  as  in  Experiment  7  (6) 
add  stannous  chloride.  Note  the  precipitation  of  thallous 
chloride  (T1C1). 

Experiment  9.  Flame  and  spectroscopic  tests  for  thal- 
lium salts,  (a)  Dip  the  end  of  a  platinum  wire  into  a  solu- 
tion of  a  thallium  salt  and  hold  it  in  the  flame  of  a  Bunsen 
burner.  Note  the  green  color. 

(fc)  Examine  spectroscopically  the  flame  colored  by  a 
solution  of  a  thallium  salt.  Observe  the  green  line. 

Experiment  10.  Negative  tests  of  thallous  salts.  Note 
that  sulphuric  acid  and  the  alkali  hydroxides  and  car- 
bonates give  no  precipitate  with  solutions  of  thallous  salts. 


CHAPTER   VI. 

TITANIUM,  Ti,  48.1. 

Discovery.  In  the  year  1791  McGregor  (Crell  Annal.  (i  791) 
I,  40,  103)  discovered  a  new  "metal"  in  a  magnetic  sand 
found  in  Menachan,  Cornwall.  This  sand  he  named  Mena- 
chinite,  and  the  newly  discovered  element  Menachite.  Four 
years  later  Klaproth  announced  the  discovery  of  a  new  earth 
in  a  rutile  which  he  was  engaged  in  studying  (Klapr.  Beitr. 
i,  233).  To  the  metal  of  this  earth  he  gave  the  name  Tita- 
nium, in  allusion  to  the  Titans.  In  1797,  however,  he 
found  that  titanium  was  identical  with  menachite  (Klapr. 
Beitr.  n,  236). 

Occurrence.  Titanium  is  found  combined  in  many 
minerals,  but  never  in  considerable  quantity  in  any  one 
locality. 

Contains  TiO2 

Rutile,  TiO2 90-100% 

Dicksbergite,  vid.  Rutile 90-100% 

Brookite,  TiO2 90-100% 

Octahedrite,  TiO2 90-100% 

Pseudobrookite,  Fe4(TiO4)3 44-  53% 

Perofskite,  CaTi03 58-  59% 

Ilmenite,  FeTiO3 3-  59% 

Magnetite,  FeO- F-2O3 o-     6% 

Bauxite,  A12O3  •  2H2O 0-4 .  5% 

Geikielite,  MgO  -TiO2 67-  68% 

Senaite,  (Fe,Pb)O-2(Ti,Mn)O2 57-  58% 

Uhligite,  Ca(Ti,Zr)O5-Al(Ti,Al)O5 48-  49% 

Arizonite,  Fe2Ti3O9 56-57% 

Molfengraaffite,  titano silicate 27-  28% 

97 


9g  THE  RARER  ELEMENTS. 

Zirkelite,  (Ca,Fe)O-2(Zr,Ti,Th)02 14-15% 

Knopite,  RO-TiO2 54-  59% 

Derbylite,  6FeO  •  sTiO2  •  Sb2O5 .   34-  35% 

Lewisite,  5CaO-2TiO2-3Sb2O5 n-  J2% 

Mauzeliite,  4(Ca,Pb)O'-TiO2-2Sb2O5 7-     8% 

Titanite,  CaTiSiO5 34-  42  % 

Neptunite,  R2RTiSi4O12 ,  17-  18% 

Keilhauite,  complex  silicate 26-  36% 

Schlormenite,  3CaO(Fe,Ti)2O3-3(Si,Ti)O2 12-  22% 

Guarinite,  CaTiSiO5 33-  34% 

Tscheffkinite,  complex  silicates 16-21% 

Astrophyllite,  (Na,K)4(Fe,Mn)4Ti(SiO4)4 7-  14% 

Leucosphenite,  Na4Ba(TiO)2(Si2O5)5 13-  14% 

Johnstrupite,  complex  silicates 7-     8% 

Mosandrite,                         "        5-  10% 

Rhonite,                 "            " 9-  10% 

Rinkite,                  "            "        13-14% 

Narsarsukite,         ' '            " 14% 

Benitoite,  BaTiSi3O9 20% 

Lorenzenite,  Na2(TiO)2Si2O7 35% 

Delorenzite,  complex 66% 

Dysanalyte,  6(Ca,Fe)TiO3-  (Ca,Fe)Nb2O6 40-  59%' 

Pyrochlore,  RNb2O6-R(Ti,Th)O3, 5-  14% 


^Eschynite,  R2Nb4O13-R2(Ti,Th)5O13 21-22% 

Polymignite,  5RTiO3-5RZrO3-R(Nb,Ta)2O6 18-19% 

Yttrocrasite,  complex  titanite 49-  50% 

Marignacite,  vid.  Pyrochlore 2—     3% 

in  in 

Euxenite,  R(NbO3) 3 •R2(TiO3)3-|H20 20-  23% 

Polycrase,  R(NbOs)8-2R(TiO8)«-3HsO 25-  29%  \ 

Blomstrandite,  complex 10-  19% 

Yttrotitanite  vid.  Keilhauite. 

Titanium  has  been  found  also  in  sand  on  the  banks  of  the 
North  Sea.  in  some  mineral  waters,  in  certain  varieties  of 


TITANIUM.  99 

coal,  in  meteorites,  and  by  means  of  the  spectroscope  it 
has  been  detected  in  the  atmosphere  of  the  sun.  It  has 
been  found  in  the  ash  of  oak,  apple,  and  pear  wood,  in 
cow  peas,  in  cotton-seed  meal,  and  in  the  bones  of  men 
and  animals.  Vid.  also  Baskerville,  Jour.  Amer.  Chem. 
Soc.  xxi,  1099. 

Extraction.      Titanium    salts    may   be    extracted    from 
rutile  by  the  following  methods: 

(1)  The  mineral  is  fused  with  three  parts  of  a  mixture 
of  sodium  and  potassium  carbonates  and  the  fused  mass 
is  extracted  with  water.     The  titanium,  as  a  sodium  or 
potassium  titanate,  remains,  together  with  some  tin  and 
iron,  in  the  insoluble  residue.     This  mass  is  treated  with 
strong  hydrochloric  acid  until  dissolved.     The  solution  is 
then  diluted,  and  the  tin  is  removed  by  hydrogen  sulphide. 
The  sulphide  of  tin  is  filtered  off,  the  filtrate  is  made  am- 
moniacal   with   ammonium   hydroxide    and    again    treated 
with  hydrogen  sulphide.     The  iron  is  precipitated  as  the 
sulphide,  and  the  titanium  as  the  hydroxide.     After  nitra- 
tion the  precipitate  is  suspended  in  water  and  a  current 
of  sulphur  dioxide  is  passed  through  until  the  black  sul- 
phide of  iron  has  dissolved,  leaving  the  oxide  of  titanium. 

(2)  The  mineral  is  fused  with  three  parts  of  acid  potas- 
sium fluoride  and  the  fused  mass  is  extracted  with  hot  water 
and  a  little  hydrofluoric  acid.     The  titanium  separates,  on 
cooling,  as  the  potassium  fluotitanate  (K2TiF6  +  H2O). 

(3)  The  mineral,  finely  pulverized,  is  fused  with  three 
times  its  weight  of  sodium  dioxide  and  the  melt  is  extracted 
with  water.     The  titanium   remains   in  solution    (H.   D. 
Newton) . 

(4)  The  mineral  is  fused  with  six  parts  of  acid  potassium 
sulphate  (vid.  Experiment  i). 

(5)  The  mineral  is  mixed  with  carbon  and  heated  in 
the  electric  furnace.*    The  carbide  thus  formed  is  con- 

*  The  mineral  ilmenite  may  be  mixed  with  sodium  sulphate  and  carbon  and 
heated  in  an  electric  furnace  (Rossi  and  Barton,  U.  S.  Patent  1,171,542,  Feb.  1916.) 


ioo  THE  RARER  ELEMENTS. 

verted  into  the  chloride  by  heating  it  with  dry  chlorine 
(Stabler,  Ber.  Dtsch.  chem.  Ges.  xxxvm,  2619). 

(6)  The  mineral  is  heated  to  1000°  and  chilled  in  water. 
The  powder  is  mixed  with  aluminum  (one-half  its  weight) 
and  ignited  by  burning  magnesium.  On  heating  the  metal 
obtained  to  a  red  heat  in  a  current  of  dry  chlorine  titanium 
tetrachloride  distils  (Ellis,  Chem.  News,  xcv,  122). 

The  Element.  A.  Preparation.  Elementary  titanium 
may  be  obtained  (i)  by  heating  potassium  fluotitanate 
with  potassium  (Berzelius  and  Wohler);  (2)  by  heating 
the  chloride  (TiCU)  in  a  bomb  with  metallic  sodium  (Hunter, 
Jour.  Amer.  Chem.  Soc.  xxxn,  330).  Vid.  also  Weiss, 
Zeitsch.  anorg.  Chem.  LXV,  345;  Zely  and  Hamburger,  ibid. 
LXXXVII,  209. 

B.  Properties.  As  prepared  by  Hunter,  titanium  resem- 
bles polished  steel.  It  is  quite  brittle  when  cold  and  readily 
malleable  at  low  red  heat.  It  does  not  decompose  water 
at  ordinary  temperatures  and  acts  on  heated  water  but 
slightly.  When  heated  in  the  air  it  combines  with  the 
oxygen,  burning  brightly  to  the  oxide  (TiO2) ;  in  oxygen 
the  combination  is  accompanied  with  brilliant  light.  Ti- 
tanium is  readily  soluble  in  warm  hydrochloric  acid,  and 
is  attacked  by  dilute  hydrofluoric,  nitric,  sulphuric,  and 
acetic  acids.  It  combines  with  chlorine.  It  combines  also 
with  n'.trogen,  forming  nitrides.  It  melts  at  1794°  C. 
(Burgess),  and  its  specific  gravity  is  4.5.  It  forms  alloys 
with  many  elements. 

Compounds.  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  titanium: 

Oxides .  .  .  TiO  ;  (Ti304) ;  Ti2O3 ;  (Ti7O12) ;  TiO2 ;  (Ti2O5) ;  TiO3 
Hydroxides  Ti(OH)4*      Ti(OH)6 

Chlorides  . .  TiCl3  TiCl4 

Bromide .  . .  TiBr4 

Iodide TiI4 

*  Orthotitanic  acid. 


TITANIUM.  I0i 

Fluoride . .  .  TiF4 
Titanofluor- 

ides R2TiF6,  etc. 

Sulphides..  Ti2S3                TiS2 

Sulphates..  Ti2(SO4)3         Ti(SO4)2 

Nitrides  * . .  Ti3N4 ;  Ti5N6 ;  TiN2 

Carbide  .  .  .  TiC 

Silicide.  .  .  .  TiSi 

Titanates  (meta)  RTiO3;  R2TiO8 

Acids  (vid.  Hydroxides)  . . .  H2Ti03 

B.  Characteristics.  Although  a  number  of  oxides  of 
titanium  are  known,  the  dioxide  is  the  form  generally 
found,  and  the  salts  of  that  type  are  by  far  the  most  numer- 
ous and  important.  The  oxide  (TiO2)  resembles  the  oxide 
of  zirconium  (ZrO2)  in  acting  as  a  weak  base.  It  forms 
salts  with  the  strong  acids,  but  does  not  combine  with  the 
weak  acids.  It  unites  with  the  strong  bases  to  form  titc  - 

nates,  (RTiO3  and  R2TiO3).  It  has  less  basic  and  more 
acidic  properties  than  the  oxide  of  zirconium.  The  tetra- 
chloride  is  a  colorless  liquid  which  fumes  in  the  air. 
Practically  all  the  salts  of  titanium  are  insoluble  in  water, 
the  presence  of  free  acid  being  necessary  to  prevent  the 
formation  of  insoluble  basic  compounds.  Titanium,  in 
its  behavior  toward  reagents,  resembles  quite  closely  both 
niobium  and  tantalum,  with  which  it  is  often  found  asso- 
ciated (vid.  Occurrence). 

Estimation. f  A.  Gravimetric.  Titanium  is  usually  pre- 
cipitated as  the  acid,  either  by  ammonium  hydroxide 
or  by  boiling  a  dilute  solution  acidified  with  acetic  or 
sulphuric  acid;  the  precipitate  is  ignited  and  the  element 
is  determined  as  the  oxide  (TiO2). 

*  Vid.  Ruff,  Ber.  Dtsch.  chem.  Ges.  XLV,  1364,  for  recent  work  on  nitrides 
and  ammono  compounds. 

t  For  estimation  in  ores,  see  Technical  Methods  of  Ore  Analysis,  Low,  John 
Wiley  &  Sons,  New  York,  1906. 


102  THE  RARER  ELEMENTS. 

B.  Volumetric.*  Titanium  is  estimated  volumetrically 
'(i)  by  treating  with  hydrogen  dioxide  a  definite  amount 
of  the  titanium  solution  to  be  determined  and  com- 
paring its  color  with  that  of  a  definite  amount  of  a 
'standard  solution  of  titanium  similarly  treated  (Weller, 
Ber.  Dtsch.  chem.  Ges.  xv,  2592);  (2)  by  reducing  the 
titanium  from  the  dioxide  to  the  sesquioxide  condition, 
by  the  use  of  zinc  and  hydrochloric  acid,  and  then  oxidiz- 
ing it  with  permanganate  (Osborn,  Amer.  Jour.  Sci.  [3] 
xxx,  329);  (3)  by  reducing  the  titanium  from  the  dioxide 
to  the  sesquioxide  condition  in  an  atmosphere  of  hydro- 
gen, by  means  of  zinc  and  sulphuric  acid,  then  oxidizing  it 
by  an  excess  of  ferric  salt,  and  estimating  the  titanium 
originally  present  by  titrating  with  potassium  permanga- 
nate the  ferrous  salt  formed  (Newton,  Amer.  Jour.  Sci. 
xxv  (1908),  130). 

Separation.  The  general  method  for  the  separation 
of  titanium  from  the  other  members  of  the  aluminum 
group  is  to  boil  dilute  acidified  solutions  (vid.  Gravimetric 
Estimation).  The  titanium  precipitate,  however,  carries 
down  traces  of  other  elements,  as  aluminum  and  iron. 

From  iron  titanium  may  be  separated  (i)  by  passing 
hydrogen  sulphide  into  an  alkaline  solution  to  which  am- 
monium tartrate  has  been  added, — the  iron  sulphide  being 
precipitated  (Gooch,  Amer.  Chem.  Jour,  vn,  283) ;  (2)  by 
treating  a  mixture  of  ferrous  sulphide  and  titanic  acid 
with  sulphur  dioxide  (vid.  Extraction) ;  (3)  by  boiling  a 
neutral  solution  with  hydrogen  dioxide, — metatitanic  acid 
being  precipitated ;  (4)  by  shaking  a  solution  of  the  chlorides 
with  ether,  the  ferric  chloride  dissolving. 

From  aluminum  titanium  may  be  separated  by  boiling 
a  solution  containing  them,  in  the  presence  of  an  alkali 
acetate  and  of  acetic  acid  to  about  seven  per  cent,  of  the 

*  Vid.  also  van  Brunt,  Jour.  Amer.  Chem.  Soc.  xxxvi,  1426;  Knecht  and 
Neumann,  Ztschr.  angew.  Chem.  xxvi,  613,  734;  xxvii,  56;  McCabe,  J.  Ind. 
Eng.  Chem.  v,  735. 


EXPERIMENTAL  WORK  ON  TITANIUM.  103 

-whole  solution, — titanium  basic  acetate  being  precipitated 
(Gooch,  Amer.  Chem.  Jour,  vn,  283). 

From  both  iron  and  aluminum  titanium  may  be  sepa- 
rated by  precipitation  with  "  cupferron  "  (Thornton,  Amer. 
Jour.  Sci.  [4]  xxxvn,  407;  Bellucci,  Gazz.  chim.  ital.  XLIII, 
I,  570).  It  may  also  be  separated  from  these  elements  as 
the  phosphate  in  acid  solution  (Jamieson  and  Wrenshall, 
J.  Ind.  Eng.  Chem.  vi,  203). 

From  cerium  and  thorium  titanium  may  be  separated  by 
precipitating  the  double  sulphates  of  those  elements  with 
potassium  sulphate.  Methods  for  the  separation  from 
zirconium  have  already  been  given  (md.  Zirconium) .  From 
niobium  and  tantalum  titanium  may  be  separated*  by 
repeated  fusions  with  acid  potassium  sulphate  and  extrac- 
tions of  the  melt  with  water, — the  titanium  being  in  soluble 
form.  A  satisfactory  separation  of  niobium  from  titanium 
may  be  effected  by  crystallizing  the  niobium-potassium 
oxyfluoride  from  35%  hydrofluoric  acid.  The  titanium 
remains  in  solution  (C.  W.  Balke  and  E.  F.  Smith,  Jour. 
Amer.  Chem.  Soc.  xxx,  1637). 

EXPERIMENTAL  WORK   ON  TITANIUM. 

Experiment  i.  Extraction  of  titanium  salts  from  rutile. 
(a)  Mix  5  grm.  of  finely  powdered  mineral  with  about  30  grm. 
of  acid  potassium  sulphate  and  fuse  until  the  mass  is  free 
f.om  black  particles.  Pulverize  the  fused  mass  and  ex- 
tract with  cold  water,  stirring  frequently  until  solution 
is  complete.  Filter,  and  to  the  filtrate  add  ammonium  sul- 
phide, filter  and  wash.  Suspend  the  precipitate,  which 
consists  mainly  of  titanium  hydroxide  and  ferrous  sulphide, 
in  water,  and  pass  a  current  of  sulphur  dioxide  through  the 
liquid,  or  add  a  solution  of  ammonium  bisulphite,  until  the 
ferrous  sulphide  has  dissolved,  as  shown  by  the  disappear- 
ance of  the.  dark  color.  Filter,  and  wash  the  titanium  hy- 
droxide which  remains. 

*  E.  F.  Smith,  Proc.  Amer.  Philos.  Soc.  XLIV  (1905),  151,  177. 


104  THE   RARER  ELEMENTS. 

(b)  Alternative  method.     After  having  dissolved  the  fused 
mass  in  cold  water  (vid.  (a))  add  about  20  grm.  of  tartaric  acid 
and  make  the  solution  faintly  ammoniacal.     Pass  hydrogen 
sulphide  until  the  iron  is  completely  precipitated.     Filter, 
add  about  10  cm.3  of  concentrated  sulphuric  acid  to  the 
nitrate,  >and  evaporate  in  a  porcelain  dish  under  a  draught 
hood    until    the    tartaric    acid    is    thoroughly    carbonized. 
Allow  the  mass  to  stand  until  cool,  add  water,  keeping  the 
liquid  cool  to  prevent  the  precipitation  of  the  titanium 
hydroxide,    and   decant   from   the   carbon  residue.     Filter 
the  brown  liquid  through  animal  charcoal  previously  freed 
from  phosphates,  and  precipitate  the  titanium  hydroxide 
with  ammonium  hydroxide  (R.  G.  Van  Name).     The  tartaric 
acid  may  be  decomposed  by  fuming  nitric  acid  and  the 
titanium    quantitatively    determined      (W.  JV1.  Thornton, 
Amer.  Jour.  Sci.  xxxiv,  214). 

Experiment  2.  Precipitation  of  titanium  hydroxide, 
(Ti(OH)4).  (a)  To  a  solution  containing  titanium  add 
sodium,  potassium,  or  ammonium  hydroxide.  Note  the 
comparative  insolubility  in  excess,  especially  in  ammo- 
nium hydroxide.  Repeat,  having  hydrogen  dioxide  present 
in  the  solution. 

(6)  Repeat  the  experiment,  using  the  alkali  carbonates. 
The  precipitate  is  the  same  as  in  (a). 

(c)  Note  the  solubility  of  the  freshly  precipitated  hy- 
droxide in  the  common  acids. 

(d)  Ignite  a  portion  of  the  precipitate  and  try  its  solu- 
bility in  acids. 

Experiment  3.  Precipitation  of  titanic  hydroxide  or 
acid  by  boiling.  (a)  Boil  a  dilute  acid  solution  of  titanic 
hydroxide.  Note  the  precipitation.  Filter,  and  test  the 
nitrate  with  ammonium  hydroxide. 

(b)  To  a  solution  of  titanic  acid  containing  enough 
free  acid  to  prevent  precipitation  on  boiling,  add  ammo- 
nium acetate.  Try  similarly  sodium  thiosulphate. 

Experiment  4.     Precipitation  of  basic  titanic  phosphate t 


GERMANIUM.  105 

(Ti(OH)PO4).  To  a  solution  containing  titanic  acid  add  a 
little  sodium  phosphate  in  solution.  Repeat,  having  hydro- 
gen dioxide  present  in  the  solution. 

Experiment  5.  Color  tests  of  solutions  containing 
titanium,  (a)  To  an  acid  solution  containing  titanium 
add  hydrogen  dioxide.  Note  the  yellow  color  (TiO3  in 
solution) . 

(b)  To  a  solution  containing  titanium  add  a  piece  of 
metallic  zinc  and  enough  acid  to  start  the  action.  Note 
the  violet  color  which  develops. 

Experiment  6.  Negative  test  of  titanium  compounds. 
Pass  hydrogen  sulphide  through  a  solution  containing, 
titanium.  Note  the  absence  of  precipitation. 


GERMANIUM,*  Ge,  72.5. 

Discovery.  In  1886  Clemens  W  inkier  announced  the 
presence  of  a  new  element  in  the  silver  mineral  argyrodite, 
which  had  been  discovered  the  previous  year  by  Weisbach, 
in  the  Himmelsfurst  mine  near  Freiberg  (Ber.  Dtsch. 
chem.  Ges.  xix,  210).  According  to  Winkler's  analysis, 
of  argyrodite,  the  sum  of  its  component  parts  was  seven  per 
cent,  less  than  it  should  have  been;  and  although  he  re- 
peated the  analysis  several  times  with  great  care,  the  out- 
come was  always  the  same.  This  uniformity  of  result  forced 
upon  him  the  conclusion  that  an  unknown  element  was 
probably  present ;  and  after  much  careful  and  patient  work 
he  was  successful  in  isolating  it  and  investigating  its  prop- 
erties. On  heating  the  mineral  out  of  contact  with  the  air, 
he  obtained  a  dark-brown  fusible  sublimate,  which  proved 
to  be  chiefly  two  sulphides,  that  of  .the  new  element,  named 
by  him  Germanium,  and  the  sulphide  of  mercury. 

*  The  discovery  of  this  element  was  predicted  by  Mendeleeff  in  1869  and  the 
hypothetical  element  was  named  Ekasilicon.  It  was  given  an  atomic  weight  of 
72,  and  a  specific  gravity  of  5.5.  Its  oxide,  chloride,  ethide,  and  fluoride,  as 
described  by  Mendeleeff,  resemble  closely  the  corresponding  compounds  of  Ge. 


ic5  THE  RARER  ELEMENTS 

Occurrence.  Germanium  is  found  in  combination  in  a 
few  rare  minerals. 

Contains 
Ge 

Argyrodite,  4Ag2S  -GeS2 6-7% 

Canfieldite,  4Ag2S-(Ge,Sn)S2 i  .82% 

Euxenite,  R(NbO3)3-R2(TiO3)3-|H2O traces 

It  occurs  also  in  some  zinc-blendes  (Urbain,*  Compt.  rend. 
CXLIX,  602 ;  CL,  1758).  It  has  recently  been  found  in  a  sul- 
phide from  Missouri,  and  in  a  blende  from  Wisconsin 
(Buchanan,  J.  Ind.  Eng.  Chem.  vm,  585). 

Bardet  *  has  found  evidence  of  its  presence  in  a  number 
of  French  mineral  waters  (Compt.  rend.  CLVII,  224).  Uhler 
has  found  it  to  be  present  also  in  the  "  leady  residue  " 
from  which  gallium  and  indium  have  been  extracted  (vid. 
page  84). 

Extraction.  Germanium  salts  have  been  extracted  as 
follows : 

(1)  A  Hessian  crucible  is  heated  to  redness,  and  small 
quantities  of  a  mixture  consisting  of  three  parts    of  sodium 
carbonate,  six  parts  of  potassium  nitrate,  and  five  parts  of 
argyrodite  are  gradually  put  in.     After  being  heated  for 
some  time  the  molten  mass  is  poured  into  an  iron  dish  and 
allowed  to  cool.     The  salt  mass  may  then  be  removed  from 
the   silver,    pulverized,    and   extracted   with   water.     The 
•extract    is    treated    with    sulphuric    acid    and    evaporated 
until  all  the  nitric  acid  is  driven  off.     The  residue  is  dis- 
solved in  water  and  allowed  to  stand  until  the  oxide  of 
.germanium  separates  from  the  solution. 

(2)  Treat  the  finely  powdered  zinc-blende  with  strong 
sulphuric    acid,    and    evaporate    to    dryness.     Dissolve    in 
water  and  add  sodium  sulphide.     Treat  the  sulphide  with 
sulphuric    acid    (15  :    100).     The    sulphide   of   germanium 

*  Urbain  obtained  5  grm.  of  germanium  from  550  kilos  of  a  Mexican  blende 
and  Bardet  0.06  grm.  of  GeO2  from  250,000  liters  of  Vichy  mineral  water. 


GERMANIUM.  io6<z 

remains,  and  the  sulphide  of  zinc  dissolves  (Urbain,  Compt. 
rend.  CL,  1758;  vid.  also  Bardet,  ibid.  CLVIII,  1278). 

(3)  The  substance  containing  germanium  is  dissolved  in 
strong  hydrochloric  acid,  and  the  solution  is  distilled  to  about 
one-half  its  volume  in  a  current  of  chlorine,*  a  condition  neces- 
sary to  keep  the  ai  senic  in  the  higher  condition  of  oxidation. 
The  germanium  is  in  the  distillate,  and  may  be  precipitated 
from  this  by  hydrogen  sulphide  in  the  presence  of  strong 
hydrochloric  acid  (Buchanan,  J.  Ind.  Eng.  Chem.  vm,  585). 

The  Element.  A.  Preparation.  Elementary  germanium 
may  be  obtained  (i)  by  heating  the  oxide  with  carbon; 
(2)  by  heating  the  oxide  in  a  current  of  hydrogen. 

B.  Properties.  Germanium  is  a  grayish- white,  metallic 
element,  having  a  fine  luster,  and  crystallizing  in  regular 
octahedra.  It  volatilizes  slightly  when  heated  in  hydrogen 
or  nitrogen  at  about  1350°  C. ;  its  melting-point  is  about 
900°  C.  In  the  air  it  does  not  oxidize  at  ordinary  tem- 
peratures, but  when  heated  goes  over  to  the  oxide  GeO,. 
It  is  not  attacked  by  dilute  hydrochloric  acid,  is  oxidized 
by  nitric  acid,  and  is  dissolved  by  aqua  regia.  It  is  dis- 
solved also  by  sulphuric  acid,  with  the  evolution  of  sul- 
phur dioxide.  It  combines  directly  with  chlorine,  bromine, 
and  iodine.  Its  specific  gravity  is  5.46. 

Compounds.  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  germanium: 


Oxides  

..GeO 

GeO2 

Chlorides  

..GeCl2 

GeCl4 

Oxy  chloride  
Bromide 

GeOCl2 
GeBr4 

Iodide            

Gel< 

GeF4;K2GeF6;   H2GeF, 

Sulphides  
Chloroform  
Ethyl 

.  .GeS 

GeS2 
GeHCl3 
Ge(C2H5)4 

'  Other  oxidizing  agents  mayalso  be  used,  such  as  potassium  permanganate  or 
potassium  chromate.    Browning  and  Scott,  Amer.  Jour.  Sci.  XLIV,  313;  XLVI,  663). 


io6b  THE  RARER  ELEMENTS. 

B.  Characteristics.  The  germanium  compounds  are 
known  in  two, conditions  of  oxidation;  those  of  the  higher 
form  are  the  more  stable  and  comprise  the  larger  group. 
Germanium  resembles  carbon  and  silicon  in  the  formation 
of  a  chloroform,  and  tin  in  the  formation  of  two  sulphides 
which  dissolve  in  ammonium  sulphide,  giving  sulpho  salts. 
The  sulphide  GeS2  is  a  white  powder  slightly  soluble  in 
water,  and  less  soluble  in  strong  hydrochloric  acid.  It  is 
soluble  in  ammonia  and  in  the  alkali  sulphides.  The  lower 
sulphide,  GeS,  when  precipitated,  is  of  a  reddish-brown  color ; 
when  obtained  by  the  reduction  of  the  higher  sulphide  it 
is  a  grayish-black  crystalline  substance  of  metallic  luster. 
This  sulphide,  also,  is  slightly  soluble  in  water.  The  dioxide 
is  a  white  powder  soluble  in  alkalies,  but  almost  completely 
insoluble  in  acids.  The  tetrachloride  is  a  liquid  which 
fumes  in  damp  air  and  is  decomposed  by  water.  A  very 
characteristic  reaction  for  this  element  is  the  precipitation 
of  gelatinous  potassium-germanium  fluoride,  K^GeFe,  by 
the  addition  of  hydrofluoric  acid  and  potassium  chloride  to 
solutions  containing  it  (Kruss  and  Nelson,  Ber.  Dtsch. 
chem.  Ges.  xx,  1696;  Buchanan,  J.  Ind.  Eng.  Chem.  vm, 
585).  Germanium  compounds  give  a  characteristic  spark 
spectrum  in  the  blue  and  violet. 

Estimation.  Germanium  is  usually  precipitated  as  the 
sulphide,  converted  by  nitric  acid  into  the  oxide  (GeO2), 
and  weighed  as  such. 

Separation.  Germanium  may  be  separated  from  most  of 
the  elements  by  the  formation  of  a  soluble  sulpho  salt  with 
ammonium  sulphide;  when  the  solution  is  acidified  the 
sulphide  is  precipitated.  Germanium  may  be  separated 
from  arsenic,  antimony,  and  tin  as  follows :  the  solution  of 
the  sulpho  salts  is  exactly  neutralized  with  sulphuric  acid, 
allowed  to  stand  twelve  hours,  and  filtered;  the  filtrate  is 
evaporated  to  a  small  volume,  treated  with  ammonia  and 
sulphate  of  ammonium,  acidified  with  sulphuric  acid,  and 
saturated  with  hydrogen  sulphide.  Germanium  sulphide 
ii  precipitated  (Truchot,  Les  Terres  Rares,  294). 


CHAPTER  VII. 

VANADIUM,  V,  51. 

Discovery.  As  early  as  1801  Del  Rio  announced  the 
discovery  of  a  new  metal  in  a  lead  ore  from  Zimapan, 
Mexico.  He  named  it  Erythronium  (epvQpos,  red),  be- 
cause its  salts  became  red  when  heated  with  acids 
(Annal.  der  Phys.  u.  Chem.  LXXI,  7).  Four  years  later 
'Collet  Descotils  examined  the  supposed  metal  and  pro- 
nounced it  an  impure  oxide  of  chromium,  —  a  conclusion 
that  Del  Rio  himself  came  to  accept  (Ann.  de  Chim.  LIII, 
268). 

In  1830  Sef  strom  found  an  unknown  metal  in  an  iron 
ore  from  Taberg,  Sweden.  He  proposed  for  it  the  name 
Vanadium,  from  Vanadis,  the  Scandinavian  goddess  more 
•commonly  known  as  Freya  (Amer.  Jour.  Sci.  [i]  xx,  386) 
Almost  immediately  Wohler  showed  the  identity  of  vana- 
dium with  the  metal  described  by  Del  Rio  (Pogg.  Annal, 
xxi,  49). 

Occurrence.  Vanadium  is  found  quite  widely  distributed, 
^always  in  combination,  and  in  very  small  quantities  : 

Contains 

VA. 

Vanadinite,  (PbCl)Pb4(VO4)3  ................  .  .  .  8-21  % 

Descloizite,  (Pb,Zn)2(OH)VO4  ...................  20-22% 

Eusynchite,  md.  Descloizite  ....................  17-24% 

Dechenite,  md.  Descloizite  ......  .  .............  45~47% 

•Cuprodescloizite,  (Pb,Zn,Cu)2(OH)VO4  .........  17-22% 

Calciovolborthite,  (Cu,Ca)2(OH)VO4  ...........  37~39% 

Carnotite*  K^ 


Amer.  Jour.  Sci.  x,  138;  xxxin,  574. 

107 


icS  THE  RARER  ELEMENTS. 

Contains  ViOi* 

Brackebuschite,  formula  doubtful 24-25% 

Psittacinite,  formula  doubtful 17-26% 

Volborthite,        "  "      14-15% 

Pucherite,  BiVO4 22-27% 

Roscoelite,  silicate,  formula  doubtful 21-29% 

Ardennite,        "  ' '        traces-g% 

Mottramite,  (Cu,Pb)5V2Oio-2H2O 17-18% 

Chileite,  vid.  Mottramite 13-14% 

Vanadiolite,  sllico-calcium  vanadate 44-45% 

Vanadic  ocher I09% 

Bismuth  ocher,  formula  doubtful 1-29%, 

Patronite,*  VS4+wS 18-19%  V. 

Sulvanite,  3Cu2S-V2S5 12-14% 

Pintadoite,  Ca2V2O7-9H2O 39-40% 

Uvanite,  (UO2)2V6Oi7-  i5H2O 3 

V204 

Minasragrite,  V2O4-3SO3-  i6H2O (24-25%) 

Fernandinite,  CaO-V2O4-5V2O5-  i4H2O  (10-11%)  5 

Hewettite,  H2CaV6Oi7-8H2O (  i-  2%)  69-70% 

Metahewettite,  vid.  Hewettite. 

Pascoite,  Ca2V6Oi--  nH20 64-65% 

Aegirite,  complex  silicate 3-  4% 

Aegirite-Augite,  complex  silicate 2-3% 

Vanadium  has  been  detected  also  in  some  copper,  lead, 
and  iron  ores,  in  certain  clays  and  basalts,  in  soda  ash  and 
phosphate  of  soda,  and  in  some  hard  coals. 

Extraction.  Vanadium  salts  may  be  extracted  from, 
mineral  sources  by  the  following  methods. 

(i)  The  mineral  is  fused  with  potassium  nitrate,  and 
the  potassium  vanadate  thus  formed  is  extracted  with  water. 
By  the  addition  of  a  soluble  lead  or  barium  salt  to  the 
solution  the  lead  or  barium  vanadate  is  precipitated.  This, 
insoluble  vanadate  is  decomposed  by  means  of  sulphuric 

*  Hillebrand,  Jour.  Amer.  Chem.  Soc.  xxix,  1019. 


VANADIUM.  109 

acid,  and  the  barium  or  lead  sulphate  is  filtered  off.  By 
saturation  of  the  filtrate  with  ammonium  chloride  the 
ammonium  vanadate  is  precipitated. 

(2)  Finely  ground  carnotite  is  decomposed  by  nitric  acid, 
and  the  solution  is  treated  with  sodium  hydroxide  and 
sodium  carbonate;  the  vanadium  is  left  in  soluble  form  as 
sodium  vanadate.     If  vanadinite  is  used  instead  of  carnotite 
the  lead  must  be  precipitated  from  the  nitric  acid  solution 
by  hydrogen  sulphide,  and  the  excess  of  hydrogen  sulphide 
removed  from  the  filtrate  by  boiling,  before  the  treatment 
with  sodium  hydroxide. 

(3)  The  mineral,    e.   g.,   carnotite,   is   fused  with   acid 
potassium  sulphate,  the  melt  extracted  with  water,  and  the 
solution  evaporated,  when  the  double  sulphates  of  vanadium 
and  uranium  with  potassium  crystallize  out.     The  vanadium 
is  reduced  by  zinc,   and  precipitated  by  ammonium   hy- 
droxide and  ammonium  carbonate. 

(4)  A    patented    process    by  J.    H.    Haynes    (Mineral 
Resources  U.  S.,  1906,  page  531)  for  treatment  of  carnotite 
is  of  interest.     The  powdered  mineral,  previously  roasted, 
is  agitated  with  boiling  sodium  carbonate,  which  extracts 
vanadium  and  uranium.     From  this  solution  the  uranium 
is  precipitated  by  sodium  hydroxide. 

The  Element.  A.  Preparation.  Elementary  vanadium 
may  be  prepared  (i)  by  the  action  of  "  mischmetal  "  (metals 
of  Ce  and  Y  groups)  on  the  oxide  (V2O5)  (Muthmann 
and  Weiss,  Liebig  Ann.,  cccxxxvn,  370;  CCCLV,  58); 
(2)  by  the  action  of  aluminum  or  carbon  on  the 
trioxide  (Ruff  and  Martin,  Zeitsch.  angew.  Chem.  xxv, 
49)- 

B.  Properties.  Vanadium  is  a  non-magnetic,  light- 
gray  powder,  somewhat  crystalline  in  appearance.  It 
oxidizes  slowly  in  the  air  at  ordinary  temperatures,  but 
more  rapidly  when  heated,  going  through  various  degrees 
of  oxidation  and  showing  a  characteristic  color  for  each 
oxide,— brown  (V2O),  gray  (V2O2),  black  (V2O3),  blue  (V2O4), 


no  THE  RARER  ELEMENTS. 

and  red  (V2O5).  Upon  the  application  of  heat  vanadium 
-unites  with  chlorine,  forming  the  chloride  VC14;  at  a  red 
heat  it  combines  with  nitrogen,  giving  the  nitride  VN.  It 
is  insoluble  in  hydrochloric  and  dilute  sulphuric  acids, 
and  soluble  in  nitric,  hydrofluoric,  and  concentrated  sul- 
phuric acids.  It  is  not  attacked  by  alkaline  solutions,  but 
with  melted  alkalies  forms  the  alkali  vanadates,  with  the 
evolution  of  hydrogen.  The  specific  gravity  of  vanadium 
is  5.68.  The  melting-point  of  the  metal  :s  1720°  C.  It 
forms  alloys  with  iron  and  aluminum. 

Compounds.*     A.    Typical  forms.      The    following   may 
be  considered  typical  compounds  of  vanadium: 


Oxides  ..........  V2O  V2O2      VzOsf             V2O4                      V2O5 

Chlorides  ........  VC12       VC13               VC1< 

Oxychlorides.  .  .  .  VOC1             VOC12 

Bromide  ........  VBr3 

Oxybromides  ----  VOBr2                    VOBr3 

Fluorides  ........  VFa+  6H2O                               VF5 

Double  fluorides.  .  VF3  with  KF,  CoF2,  NiF2,  etc. 

Sulphides  .......  VjSj       V2S3                                           V2S3O2 

V2S5 

Sulpho  salts  .....  Na3VS3O 

(NH4)3VS4)  etc. 

Sulphate  ........  VSO<        V^SOJ  K3SO4+24H,O           VACSOJ, 

Nitrides  .........  VN                                              VN2 

Vanadates,  ortho,  R3VO4 

pyo,  R4V207 


complex,    V2O5  with  P2O5,  MoO3,  WO3,  SiO2,  AsO5,  etc. 

B.    Characteristics.      The     vanadium     compounds     are 
known  in  five  conditions  of  oxidation,  represented  by  the 

*  See  also  Das  Vanadin  und  seine  Verbindungen,  Ephraim,  pub.  by  Ferdi- 
nand Enke,  Stuttgart,  1904;  Riitter,  Zeitsch.  anorg.  Chem.  LII,  368;  Prandtl, 
Ber.  Dtsch.  chem.  Ges.  XL,  2125;  XLVTII,  692;  Ztschr.  anorg.  chem.  LXXXTI,  103; 
Koppel,  Zeitsch.  Electrochem.  x,  141  ;  Wedekind,  Ber.  Dtsch.  chem.  Ges.  XLVI, 
1885,  1198;  Barbieri,  Atti  accad.  Lincei  xxrv,  1,  435;  Ruff,  Ber.  Dtsch.  chem._Ges. 

XLIV,  506,  2534. 

f  Dutton  (Jour.  Amer.  Med.  Asso.,  June  3,  1911)  describes  a  new  form  of  poison- 
ing called  Vanadiumism,  caused  by  exposure  to  the  fumes  of  vanadium  trioxide. 


VANADIUM.  m 

•five  oxides.  Of  these  conditions  the  highest  is  the  most 
stable  and  is  known  in  the  largest  number  of  salts,  the 
vanadates.  Vanadic  pentoxide  is  reddish  yellow  in  color, 
and,  like  phosphoric  pentoxide,  it  dissolves  readily  in  the 
alkali  hydroxides  and  carbonates.  The  alkali  vanadates 


thus  formed  are  of  the  ortho,  pyro,  and  meta  types,  (RgVO4 ; 

RV2O7;  RVO3).  The  vanadates  are  generally  pale  yellow 
in  color.  They  are  soluble  IA  the  stronger  acids  and  with 
the  exception  of  the  alkali  vanadates  insoluble  in  water. 
Vanadic  acid  is  easily  reduced  by  reducing  agents  to  the 
tetroxide  condition,  when  the  solution  become  blue.  More 
powerful  reducing  agents  carry  the  reduction  further,  to 
the  trioxide,  or  even  the  dioxide  condition,  but  only  long- 
continued  heating  in  a  current  of  hydrogen  brings  about 
the  reduction  to  the  monoxide  and  the  element. 

Hydrogen  sulphide,  acting  upon  vanadic  acid,  reduces 
it  to  the  tetroxide  condition  or  even  below,  with  a  sepa- 
ration of  sulphur.  Ammonium  sulphide  gives  the  dark- 
brown  solution  of  a  sulpho  salt,  ((NH4)3S3VO?),  and  this 
solution,  when  acidified,  gives  a  brown  oxysulphide  (V2S3O2). 
Vanadium  resembles  arsenic,  phosphorus,  and  nitrogen, 
both  in  the  chemical  structure  of  its  compounds  and  in 
their  behavior  toward  reagents. 

Estimation.*  A.  Gravimetric.  Vanadium  is  usually 
weighed  as  the  pentoxide,  (V2O5),  obtained  (i)  by  precipi- 
tation of  lead  or  barium  vanadate,  treatment  with  sulphuric 
acid,  filtration,  evaporation  of  the  filtrate,  and  ignition;  (2) 
by  precipitation  of  mercury  vanadate  and  ignition,  the 
pentoxide  being  left;  (3)  by  precipitation  of  the  ammo- 
nium salt  by  ammonium  chloride  and  ignition  (Berzelius, 
Pogg.  Annal.  xxn,  54;  Gibbs,  Amer.  Chem.  Jour,  v,  371; 

*  See  Die  analytische  Chemie  des  Vanadins,  V.  von  Klecki,  pub.  by  Leopold 
Voss,  Hamburg,  1894;  Campagne,  Ber.  Dtsch.  chem.  Ges.  xxxvi,  3164;  Beard, 
Ann.  Chim.  anal,  et  appl.  x,  41;  Chem.  Zentr.  1905  [i],  960.  For  estimation 
in  ores,  see  also  Low's  Technical  Methods  of  Ore  Analysis;  Blair,  Jour.  Amer. 
Chem.  Soc.  xxx,  1229;  Campbell,  ibid,  xxx,  1233. 


112  THE  RARER  ELEMENTS. 

Gooch  and  Gilbert,  Amer.  Jour.  Sci.  [4]  xiv,  .205) ;  or  (4)  by 
precipitation  with  "  cupf erron  "  (Turner,  ibid.  XLI,  339). 

B.  Volumetric.  Vanadium  may  be  estimated  volu- 
metrically  (i)  by  reduction  from  the  condition  of  the  pent- 
oxide  to  that  of  the  tetroxide  by  sulphur  dioxide,  hydro- 
gen sulphide,  or  zinc  and  free  acid,  and  reoxidation  by 
permanganate  (Hillebrand,  Jour.  Amer.  Chem.  Soc.  xx, 
461;  Gooch  and  Gilbert,  Amer.  Jour.  Sci.  [4]  xv, "  389) ; 

(2)  by  effecting  the  reduction  by  boiling  with  hydrochloric 
acid  or  with  potassium  bromide  or  iodide  in  acid  solution, 
according    to    the    typical    equation   V2O5+  2HC1=V2O4+ 
H2O+C12.     The  chlorine,  bromine,  or  iodine  may  be  dis- 
tilled and  determined  by  suitable  means  in  the  distillate 
(Holverscheit.  Dissertation,  Berlin,  1890;    Friedheim,  Ber. 
Dtsch.  chem.  Ges.  xxvm,  2067;    Gibbs,  Proc.  Amer.  Acad. 
x,  250;  Gooch  and  Stookey,  Amer.  Jour.  Sci.  [4]  xiv,  369; 
Gooch  and  Curtis,  Amer.   Jour.   Sci.  [4]  xvii,  4),   or   the 
residue  after  boiling  may  be  rendered  alkaline  by  potas- 
sium  bicarbonate,   and   reoxidation  effected  by  standard 
iodine  solution  (Browning,  Amer.  Jour.  Sci.  [4]  n,    185); 

(3)  the  reduction  may  be  accomplished  by  boiling  with 
tartaric,  oxalic,  or  citric  acid,  and  reoxidation  effected  as 
outlined  above  (Browning,  Zeitsch.  anorg.  Chem.  vn,  158, 
and  Amer.  Jour.  Sci.  [4]  n,  355) ;   (4)  or  sodium  thiosulphate 
may  be  the  reducing  agent  (Oberhelman,  Amer.  Jour.  Sci. 
xxxix,   530).     (5)    Vanadium   and    molybdenum    may   be 
estimated  when  together  by  heating  their  acids  in  the  pres- 
ence of  sulphuric  acid  and  treating  with  sulphur  dioxide, 
which  reduces  the  vanadium  to  the  condition  of  the  tetroxide,, 
without  affecting  the  molybdic  acid.     The  vanadium  may 
be  estimated  as  in   (i)   by  permanganate.     The  oxidized 
solution  may  then  be  passed  through  a  Jones  reductor  into 
a  receiver  charged  with  a  ferric  salt.     This  process  reduces 
the  molybdenum  to  the  sesquioxide  (Mc^Os)  condition  and 
the  vanadium  to  the  dioxide  (V2O2)  condition,  and  registers 
the  reduction  in  the  ferric  salt.     The  reoxidation  is  again 


VANADIUM.  113 

effected  with  permanganate  and  the  amount  of  vanadium 
being  known  from  the  first  titration  the  molybdenum  may 
be  calculated  from  the  second  (Edgar,  Amer.  Jour.  Sci.  xxv,. 
(1908),  332).  (6)  By  a  similar  process  of  differential  re- 
duction and  oxidation  Edgar  (Amer.  Jour.  Sci.  xxvi,  (1908), 
79),  estimates  iron  and  vanadium  in  the  presence  of  each 
other.  After  the  solution  containing  vanadic  acid  and  iron 
has  been  reduced  by  sulphur  dioxide  the  oxidation  by  per- 
manganate proceeds  according  to  the  equation : 


After  the  reduction  by   zinc  in  the  Jones  reductor   the 
oxidation  is  as  follows: 


From  these  equations,  the  amount  of  permanganate  used 
being  known,  the  amount  of  iron  and  vanadium  present 
may  be  calculated. 

Separation.  Vanadium  may  be  separated  from  the 
majority  of  the  metallic  bases  (i)  by  fusion  of  material 
containing  it  with  sodium  carbonate  and  potassium  nitrate 
and  extraction  with  water,  vanadium  dissolving  as  sodium 
vanadate  ;  or  (2)  by  treatment  of  a  solution  containing 
a  vanadate  with  ammonium  sulphide  in  excess,  vanadium 
remaining  in  solution  as  a  sulpho  salt. 

From  arsenic  vanadium  may  be  separated  (i)  by  treat- 
ment with  hydrogen  sulphide,  after  reduction  by  means 
of  sulphur  dioxide,  the  arsenic  being  precipitated  as  the 
sulphide  As2S3;  (2)  by  heating  the  sulphides  of  vanadium 
and  arsenic  in  a  current  of  hydrochloric-acid  gas  at  150°  C., 
the  arsenic  forming  a  volatile  compound  (Field  and  Smith, 
Jour.  Amer.  Chem.  Soc.  xvm,  1051). 

From  phosphorus  vanadium  may  be  separated  by  re- 
duction of  vanadic  acid  by  means  of  sulphur  dioxide,  and 
precipitation  of  the  phosphorus  as  phosphomolybdate. 


114  THE  RARER  ELEMENTS. 

From  molybdenum  the  separation  may  be  accomplished 
by  the  action  of  hydrogen  sulphide  upon  a  solution  of  vana- 
dic  and  molybdic  acids  under  pressure, — molybdenum  sul- 
phide being  precipitated, — or  by  the  action  of  ammonium 
chloride  in  excess  upon  a  solution  containing  an  alkali 
vanadate  and  molybdate, — ammonium  metavanadate  being 
precipitated  (Gibbs,  Amer.  Chem.  Jour,  v,  371). 

From  tungsten  vanadium  may  be  separated  by  the 
ammonium  chloride  method  (vid.  Separation  from  molyb- 
denum, above)  (Gibbs,  Amer.  Chem.  Jour,  v,  379). 

From  uranium  vanadium  may  be  separated  (i)  by 
sodium  hydroxide,  as  in  Experiment  i;  (2)  by  treatment 
with  chlorine  (Barker  and  Schmidt,  Met.  Chem.  Eng.  xiv, 
18). 

EXPERIMENTAL  WORK  ON  VANADIUM. 

Experiment  i.  Extraction  of  vanadium  from  carnotite. 
Treat  20  grm.  of  the  finely  powdered  mineral  with  hydro- 
chloric acid,  heat  until  nothing  further  dissolves,  dilute, 
pass  hydrogen  sulphide,  and  filter.  Evaporate  the  filtrate 
nearly  to  dryness,  add  enough  nitric  acid  to  oxidize  the 
vanadium  to  vanadic  acid.  To  the  oxidized  solution  add 
sodium  hydroxide  in  excess,  warm,  and  filter.  The  filtrate 
should  contain  sodium  vanadate  together  with  an  excess  of 
sodium  hydroxide.  Neutralize  carefully  with  acetic  acid' 
and  test  for  vanadium  by  any  of  the.  folio  wing  experiments' 

Experiment  2.     Formation  of  insoluble  vanadates  of  lead, 

ii  ii 

silver,  barium  and  ammonium,  (RsCVO^,  ortho;  or  R(VOs)2, 
metd). 

To  separate  portions  of  a  solution  of  an  alkali  vanadate 
(ortho  or  meta)  add  (a)  a  solution  of  lead  acetate;  (6) 
silver  nitrate;  (c)  barium  chloride;  (d)  ammonium  chloride 
(in  solid  form).  Try  the  action  of  nitric  and  acetic  acids 
upon  the  precipitated  salts. 

Experiment  3.     Formation  of  vanadium  pentoxide, 


EXPERIMENTAL   WORK  ON  VANADIUM.  115 

from  ammonium  vanadate.  Evaporate  a  solution  of  am- 
monium vanadate  to  dryness  and  ignite.  Note  the  crystals 
of  the  pentoxide. 

Experiment  4.  Precipitation  of  vanadium  oxy sulphide, 
(¥28302).  (a)  To  a  solution  of  an  alkali  vanadate  add 
ammonium  sulphide.  Note  the  darkening  in  color 
((NH4)3S3VO?).  Acidify  the  solution  with  hydrochloric 
acid.  Note  the  precipitation  of  the  oxysulphide. 

(6)  Note  that  hydrogen  sulphide  in  an  acid  solution 
precipitates  sulphur  and  leaves  a  blue  solution  (V2O4). 

(c)  Pass  hydrogen  sulphide  into  a  solution  of  a  vanadate 
made  strongly  alkaline  with  ammonium  hydroxide.  Note 
the  red  color. 

Experiment  5.  Reduction  of  vanadic  acid,  (V205). 
(a)  To  a  solution  of  an  alkali  vanadate  add  a  crystal  of 
tartaric  acid  and  boil.  Note  the  yellow-red  color  of  the 
vanadic  acid  when  the  tartaric  acid  is  first  added,  and 
the  change  to  blue  (V204)  produced  on  boiling. 

(6)  Neutralize  the  blue  solution  obtained  in  (a)  with 
sodium  or  potassium  bicarbonate,  and  add  a  solution  of 
iodine  in  potassium  iodide  until,  after  the  liquid  has  stood 
for  a  few  moments,  the  color  of  the  iodine  remains.  Bleach 
the  excess  of  iodine  with  an  alkaline  solution  of  arseniou3 
oxide.  Note  that  the  blue  color  has  disappeared  and  the 
vanadium  is  in  the  condition  of  the  pentoxide  (V2O5). 

(c)  Try  the  action  of  other  reducing  agents  upon  vanadic 
acid,  e.g.  oxalic  acid,  'hydrochloric  acid,  stannous  chloride, 
zinc  and  hydrochloric  acid,  etc.  Note  that  the  zinc  and 
hydrochloric  acid  carry  the  reduction  below  the  tetroxide 
condition  (V204)  * 

Experiment  6.  Delicate  tests  for  vanadium.  Formation 
of  pervanadic  acid,  (HVO4).  (a)  Acidify  a  solution  of  an 

*  The  following  series  of  colors  obtained  by  the  action  of  a  reducing  agent 
upon  vanadic  acid  is  given  by  Roscoe:  yellow  (V2O5),  green  (V2O5+V2O4),  bluish- 
green  (V2O5+V2O4),  blue  (V2O4),  greenish-blue  (V2O4+V2O3),  green  (V2O3+V2O2), 
bluish-violet  (V2Os+V2O2),  lavender  or  violet  (V2O2). 


Ii6  THE  RARER  ELEMENTS. 

alkali  vanadate  and  add  hydrogen  dioxide.  Note  the  red 
color  (Maillard). 

(6)  Bring  a  few  drops  of  the  vanadium  solution  into 
contact  with  a  drop  of  strong  sulphuric  acid  to  which  a 
crystal  of  strychnine  sulphate  has  been  added.  Note  the 
color,  changing  from  violet  to  rose. 

Experiment  7.  Borax-bead  tests  for  'vanadium.  Fuse  a 
little  ammonium  vanadate  into  a  borax  bead  and  test  the 
action  of  the  reducing  and  oxidizing  flames  upon  it. 

NIOBIUM   (COLUMBIUM),  Nb(Cb),  93.5; 
TANTALUM,  Ta,  181.5. 

Discovery.  Hatchett,  while  working  with  some  chro- 
mium minerals  in  the  British  Museum  in  1801,  came  across 
a  black  mineral  very  similar  to  those  upon  which  he  was 
engaged  (Phil.  Trans.  Roy.  Soc.  (1802),  49).  He  obtained 
permission  to  examine  it  and  found  it  to  consist  almost 
wholly  of  iron  and  an  earth  which  did  not  conform  to 
any  known  test.  He  described  it  as  "a  white,  tasteless 
earth,  insoluble  in  hot  and  cold  water,  acid  to  litmus, 
infusible  before  the  blowpipe,  and  not  dissolved  by  borax. ' ' 
The  only  acid  which  dissolved  it  was  sulphuric.  Since 
the  mineral  was  of  American  origin,  coming  from  Con- 
necticut, the  discoverer  named  it  Columbite,  and  the 
element  Columbium. 

About  a  year  later  Ekeberg  (Crell  Annal.  (1803)  i,  3), 
while  investigating  a  mineral  from  Kimito,  Finland,  which 
closely  resembled  columbite,  discovered  a  "metal"  which 
resembled  tin,  tungsten,  and  titanium.  It  proved  to  be 
none  of  these,  but  in  fact  a  new  element.  He  named  it 
Tantalum,  "because  even  when  in  the  midst  of  acid  it 
was  unable  to  take  the  liquid  to  itself. ' '  Indeed,  insolu- 
bility in  acid  seemed  to  be  the  chief  characteristic  of  the 
new  substance. 

The  apparent  similarity  of  columbium  and  tantalum, 
suggested  that  they  might  be  identical,  and  in  order  to 


NIOBIUM   (COLUMBIUM);   TANTALUM.  117 

settle  this  question  Wollaston  (Phil.  Trans.  Roy.  Soc. 
xcix,  246)  in  1809  began  to  work  on  tantalite  and  a  speci- 
men of  the  same  columbite  that  Hatchett  had  examined. 
He  found  that  the  freshly  precipitated  acids  were  both 
soluble  in  concentrated  mineral  acids;  if  they  were  dried 
it  was  necessary  to  fuse  them  both  with  caustic  alkalies 
before  they  could  be  dissolved.  Both  were  held  up  if 
ammonium  hydroxide  was  added  in  the  presence  of  citric, 
tartaric,  or  oxalic  acid.  Having  found  practically  the  same 
reactions  with  both  acids,  he  concluded  that  the  elementary 
substances  were  the  same.  The  specific  gravity  of  tantalite, 
however,  was  7.95,  and  that  of  columbite  5.91.  This  he 
explained  by  suggesting  different  conditions  of  oxidation 
or  different  states  of  molecular  structure.  These  con- 
clusions were  accepted,  and  for  many  years  the  element 
vas  called  indifferently  tantalum  and  columbium. 

In  1844  Rose  began  to  investigate  the  same  subject. 
His  work  on  the  columbites  of  Bodenmais  and  Finland 
led  him  to  the  belief  that  there  were  two  distinct  acids 
in  the  columbite  from  Bodenmais,  one  similar  to  that  in 
tantalite,  the  other  containing  a  new  element,  to  which 
he  gave  the  name  Niobium,  from  Niobe,  daughter  of  Tan- 
talus. Though  niobium  proved  to  be  Hatchett's  colum- 
bium, Rose's  name  for  the  element  has  been  the  one  more 
generally  adopted.  The  name  columbium  is  now,  however, 
growing  in  favor,  especially  among  American  chemists. 

Occurrence.*  Niobium  and  tantalum  are  found,  each 
in  combination,  in  various  rare  minerals.  They  usually, 
though  not  invariably,  occur  together. 

Contains 
Nb205  Ta206 

Pyrochlore,  RNb2O6-R(Ti,Th)03 47-58% 

Chalcolamprite,  vid.  Pyrochlore 5  9-60% 

Marignacite,  vid.  Pyrochlore 55-56%  5-  6% 

Koppite,  R2Nb2O7-|NaF 61-62% 

*  See  also  Schilling,  Zeitsch.  angew.  Chem.  (1905),  883. 


n8  THE  RARER  ELEMENTS. 

Contains 
Nb205  Ta206 

Hatchettolite,2R(Nb,Ta)206-R2(Nb,Ta)207  63-67%* 

Microlite,  Ca2Ta2O7 7~  8%  68-69% 

Fergusonite,  (Y,Er,Ce)(Nb,Ta)O4 14-46%    4~43% 

Samiresite,  complex 45-46%  3-  4% 

Blomstrandine-Priorite,  complex 18-37%     0-1% 

Sipylite,  RNb04 47-48%     i-  2% 

Co/«m6*fe,(Pe,Mn)(Nb,Ta)aOe 26-77%     i~77% 

Tantalite,  FeTa2O6 3-40%  42-84% 

Neotantalite,  vid.  Tantalite 23%  60-61% 

Skogbolite,  FeTa206 3-40%  42-84% 

Tapiolite,  Fe(Nb,Ta)206 11-12%  73~74% 

Mossite,  Fe(Nb,Ta)206 83% * 

Yttrotantalite,  RR2(Ta,Nb)4Oi5 12-13%  46-47% 

Samarskite,  R2R3(Nb,Ta)6O2i 41-56%  14-27% 

Nohlite,  vid.  Samarskite 50-51% 

Loranskite,  complex 47% 

Risorite,  yttrium  niobate 36-37%         4% 

Stibiotantalite,  Sb2O3(Ta,Nb)2O5? 7  •  5  %         5*% 

Annerodite,  complex 48-49% 

Hielmite,  complex 4-16%   55~72% 

^schynite)R2Nb4013-R2(Ti,Th)5013 32-33%  21-22% 

Polymignite, 

5RTiO3-5RZrO3-R(Nb,Ta)2O6 11-12%     1-2% 

Euxenite,  R(NbO3)3-R2(TiO3)3.|H20 18-35% 

Polycrase,  R(NbO3)3-2R2(TiO3)3-3H2O  .  .  .    19-25%     o-  4% 

Wohlerite,  i2R(Si,Zr)O3-RNb2O6 12-14% 

Lavenite,  R(Si,Zr)O3-Zr(SiO3)2-RTa2O6.  .     o-  5%* 

Dysanalyte,  6RTiO3  •  RNb2O6 0-23%     0-5% 

Kochelite,  vid.  Fergusonite 29-30% 

Arrhenite,  complex 2-  3%  21-22% 

*  Nb2O6+Ta2O6. 


NIOBIUM  (COLUMBIUM);   TANTALUM. 

Contains 


Blomstrandite,  complex  .................  49-50%* 

Rogersite,  ..............................  1  8-20% 

Adelpholite,  vid.  Sipylite  ................  41-42%* 

Vietingshofite,  vid.  Samarskite  ...........  51  %* 

Eucolite,  complex  silicates  ...............  2-  4%* 

Melanocerite,  complex  silicates  ...........  3-  4% 

Caryocerite,  vid.  Melanocerite  ............  3-i% 

Steenstrupine,  vid.  Melanocerite  ..........  0-1.5%* 

Cyrtolite,  silicate  ........................  0-1.5%* 

Naegite,  silicate  .........................  4%          7% 

Tritomite,  complex  silicates  ..............  1-3% 

Cassiterite  (Ainalite),  Sn02  ..............  o-  9% 

Extraction.  Salts  of  niobium  and  tantalum  may  be 
extracted  from  columbite  or  tantalite  by  either  of  the  fol- 
lowing methods  : 

(1)  The  mineral  is  fused  with  six  parts  of  potassium 
bisulphate,  the  fused  mass  is  pulverized  and  treated  with 
hot   water  and  dilute  hydrochloric  acid.      The  residue  is 
then  digested  with  ammonium  sulphide  to  remove  tin,  tung- 
sten, etc.,  and  again  warmed  with  dilute  hydrochloric  acid. 
After  this  treatment  it  is  washed  thoroughly  with  water 
and  dissolved  in  hydrofluoric  acid.     Filtration  is  followed 
by  the  addition  of  potassium  carbonate  to  the  clear  solu- 
tion until  a  precipitate  begins  to  form.     The  potassium 
and  tantalum   double   fluoride    separates   first   in   needle- 
like   crystals,  after  which  the   niobium  oxyfluoride  crys- 
tallizes in  plates. 

(2)  The  mineral  is  fused  with  three  parts  of  acid  potas- 
sium fluoride  (vid.  Experiment  i). 

The  Elements.  I.  NIOBIUM.  A.  Preparation.  The  ele- 
ment niobium  may  be  obtained  (i)  by  reducing  the  oxide 
with  aluminum  (Goldschmidt  reaction)  ;  (2)  by  mixing  the 
pentoxide  with  paraffin,  drawing  into  fibers,  and  reducing 


I20  THE  RARER  ELEMENTS. 

to  the  tetroxide  by  heating  with  carbon.  The  tetroxide, 
being  a  conductor,  is  reduced  to  the  metal  by  heating 
highly  in  vacua  (von  Bolton,  Zeitsch.  Electrochem.  xm, 
145);  (3)  by  heating  the  oxide  with  "  mischmetal" 
(Muthmann  and  Weiss,  Liebig  Ann.  cccxxxvn,  370;  CCCLV, 

58). 

B.  Properties.  Niobium  is  a  metallic  element  of  steel- 
gray  color  and  brilliant  luster.  Heated  in  the  air  it  is 
only  slowly  oxidized  to  Nb2O4.  It  is  practically  unattacked 
by  acids,  except  by  a  mixture  of  nitric  and  hydrofluoric 
acids,  but  is  attacked  by  fused  alkalies  and  at  red  heat  by 
chlorine.  It  combines  with  hydrogen  and  nitrogen.  It 
is  as  hard  as  wrought  iron,  and  is  malleable  and  ductile.  Its 
fusing-point  is  1950°  C.,*and  its  specific  gravity  is  about  7. 

II.  TANTALUM. f  A.  Preparation.  Elementary  tanta- 
lum may  be  obtained  (i)  by  heating  the  potassium  and 
tantalum  fluoride  (K2TaF7)  with  potassium  and  extract- 
ing the  potassium  fluoride  with  water;  (2)  by  heating  the 
oxide  with  "mischmetal." 

B.  Properties.  Tantalum  in  the  elementary  condition 
is  a  little  darker  in  color  than  platinum,  and  is  about  as 
hard  as  soft  steel.  It  can  be  hammered  into  plates  and 
drawn  into  wire.  In  the  cold  it  is  very  inert.  Heated  to 
400°  C.  it  becomes  yellow,  and  to  600°  bluish.  At  low 
redness  it  burns  to  the  oxide.  Its  melting-point  is  given  as 
2850°  C.  (von  Pirani)jmd  2900°  C.  (Waidner).  J  It  combines 
at  low  redness  with  hydrogen,  §  nitrogen,  and  chlorine.  It 
combines  readily  with  carbon,  forming  several  carbides. 
The  metal  is  not  attacked  by  hydrochloric,  nitric,  or  sul- 
phuric acid,  but  is  attacked  by  hydrofluoric  acid  and  by 
fused  alkalies.  The  specific  gravity  of  melted  and  drawn 

*  U.  S.  Bureau  of  Standards  gives  1700°  C.  ? 

fVon  Bolton,  Zeitsch.  angew.  Chem.  (1906),  1537;  Muthmann,  Liebig  Ann. 
CCCLV,  58. 

J  Waidner  and  Burgess,  J.  physique  vi,  380;  Chem.  Abs.,  Amer.  Chem.  Soc. 
n,  739  (Mar.  '08);  von  Pirani  and  Meyer,  Zeitsch.  f.  Electrochem.  xvn,  908. 

§  Sieverts  and  Bergner,  Ber.  Dtsch.  chem.  Ges.  XLIV,  2394. 


NIOBIUM  (COLUMBWM);  TANTALUM.  I2i 

tantalum  is  16.8;  that  of  the  metal  in  powder  form  (hydro- 
gen and  oxygen  being  present),  14. 

Compounds.*    A.  Typical  forms.     The  following  are  typ- 
ical compounds  of  niobium  and  tantalum  : 
Oxides  ..........  Nb2O2 

Nb2O4  Ta204 

Nb2O5  Ta2O5 

Chlorides  .......  (Nb6Cli2)Cl2-7H2Ot  (Ta6Cli2)Cl2-7H2Ot 

NbCl3 

NbCl5  TaCl5 

Oxychloride  .....  NbOCl3 

Bromides  .......  NbBr5  TaBr5 

Oxybromide  .....  NbOBr3 

Fluorides  .......  NbF5  TaF5 

Oxyfluoride  .....  NbOF3 

Fluotantalates  .  .  K2TaF7 

Na2TaF7 
(NH4)2TaF7 
Double  fluorides  .     xKF  .yNbOF3  ) 


Sulphide  ........       Nb2OS3  Ta2S4 

Silicide  .........  TaSi2 

Nitride  ..........  Ta3N8 

Niobates  ........     K8Nb6O19  +  1  6H,O 

K6Nb4013  +  i3H20 
2K,Nb4On-fnH2O 


Na18Nb14043 
Na2Nb2O6,  etc. 

Tantalates  J  ____  Of  types  R8Ta6O19  and  RTaO3, 

with  Na,  K,  NH4,  Ba,  and  Mg. 

*  See  also  E.  F.  Smith  and  others,  Jour.  Amer.  Chem.  Soc.  xxvn,  1140,  1216, 
1369;  xxx,  1637;  xxxn,  323,  729;  Chabrie,  Compt.  rend.  CXLIV,  804;  Ruff  and 
Schiller,  Zeitsch.  anorg.  Chem.  Lxn,  329. 

t  For  corresponding  bromides  and  iodides,  vid.  (for  niobium)  Harned,  Jour. 
Amer.  Chem.  Soc.  xxxv,  1078;  (for  tantalum)  Chapin,  ibid,  xxxn,  323. 

J  Vid.  also  Wedekind  and  Maass,  Zeitsch.  angew.  Chem.  xxxm,  2314. 


122  THE  RARER  ELEMENTS. 

B.  Characteristics.  The  compounds  of  niobium  closely 
resemble  those  of  tantalum,  both  in  chemical  form  and  in 
behavior  toward  reagents.  The  two  elements  are  closely 
associated  in  minerals  (vid.  Occurrence) .  The  lower  oxides 
of  niobium  are  dark  powders  which  oxidize  when  heated. 
The  dioxide  is  soluble  in  hydrochloric  acid,  while  the  tetrox- 
ide  is  not  attacked  by  acids.  The  pentoxide  is  a  yellowish- 
white  amorphous  powder  somewhat  soluble  in  concen- 
trated sulphuric  acid  before  ignition,  but  insoluble  after. 
Niobium  pentachloride  is  a  yellow  crystalline  substance 
prepared  by  passing  sulphur  chloride  (S2C12)  in  the  form  of 
vapor  over  the  pentoxide.  It  tends  to  form  the  oxy- 
chloride  in  the  presence  of  water.  It  is  reduced  to  the 
trichloride  when  its  vapor  is  passed  through  a  red-hot  tube. 
The  fluoride  is  formed  by  the  action  of  hydrofluoric  acid 
upon  the  pentoxide 

Tantalum  tetroxide  is  a  very  hard,  dark-gray,  porous 
mass  which  is  not  attacked  by  acids.  When  heated  it 
goes  over  to  the  higher  oxide.  The  pentoxide  of  tanta- 
lum is  a  white  powder  which  is  somewhat  soluble  in  acids. 
The  chloride  and  fluoride  of  tantalum  are  formed  similarly 
to  the  corresponding  salts  of  niobium  and  resemble  them 
in  general  behavior.  Niobates  and  tantalates  are  obtained 
by  fusing  the  oxides  with  caustic  alkalies;  these  salts  are 
soluble.  The  tantalum  compounds  give  no  color  test  with 
morphia,  tannic  acid,  or  pyrogallic  acid. 

Estimation.  A.  Gravimetric.  Niobium  and  tantalum 
are  ordinarily  weighed  as  the  oxides  Nb2O5  and  Ta2O5> 
obtained  from  ignition  of  the  acids. 

B.  Volumetric.  Niobium  may  be  estimated  volumet- 
rically  by  reduction  from  the  condition  of  the  pentoxide  to 
that  of  the  trioxide  by  means  of  zinc  and  hydrochloric 
acid  in  a  current  of  carbon  dioxide,  and  oxidation  with 
permanganate  (Osborn,  Amer.  Jour.  Sci.  [3]  xxx,  329; 
Levy,  Analyst.  XL,  204.  Vid.  also  Meimberg,  Ztschr. 
angew.  Chem.  xxvi,  83). 

Separation.     The    method    usually    employed    for    the 


EXPERIMENTAL    WORK  ON  NIOBIUM  AND  TANTALUM.      123 

separation  of  niobium  and  tantalum  from  the  elements 
with  which  they  are  generally  associated — namely,  tita- 
nium, zirconium,  and  thorium — is  that  of  fusion  with  acid 
potassium  sulphate  (vid.  Titanium).  From  tin  and  tung- 
sten they  may  be  separated  by  repeated  fusions  of  the 
oxides  with  sodium  carbonate  and  sulphur  (E.  F.  Smith, 
Proc.  Amer.  Philos.  Soc.  XLIV,  157). 

The  separation  of  niobium  from  tantalum  is  one  of 
the  most  difficult  of  analytical  problems.  Marignac's 
method*  (Ann.  Chim.  Phys.  [4]  vin,  i)  is  based  upon  the 
difference  in  solubility  f  between  the  tantalum-potassium 
fluoride  (IGTaF-)  and  the  niobium-potassium  oxyfluoride 
(2KF-NbOF3+H2O).  Foote  and  Langley  (Amer.  Jour. 
Sci.  [4]  xxx,  393)  have  devised  an  indirect  method  depend- 
ing upon  the  difference  in  density  (Ta2Os,  8.716  and 
NboOs,  4.552)  of  the  oxides.  They  use  as  standards  for 
comparison  densities  of  mixtures  of  known  content. 

EXPERIMENTAL    WORK    ON    NIOBIUM    AND 
TANTALUM. 

Experiment  i.  Extraction  of  niobium  and  tantalum 
salts  from  columbite  or  tantalite.  Mix  5  grm.  of  the  finely 
ground  mineral  with  15  grm.  of  acid  potassium  fluoride 
and  fuse  thoroughly.  Pulverize  the  fused  mass  and  extract 
with  boiling  water  containing  a  little  hydrofluoric  acid. 
Evaporate  to  about  200  cm.3  and  allow  the  liquid  to  stand. 
The  potassium  and  tantalum  fluoride  separates  first  in 
needle-like  form;  the  niobium  and  potassium  oxyfluoride 
crystallizes  in  plates  on  concentration  of  the  solution. 
The  salts  of  the  two  elements  should  be  purified  as  far  as 
possible  by  fractional  crystallizations. 

Experiment  2.  Preparation  of  niobic  and  tantalic 
oxides  (acids),  (Nb20s;  T^Os).  (a)  Evaporate  to  dryness 

*  Vid.  Meimberg  and  Winzer,  Ztschr.  angew.  Chem.  xxvi,  157;  Moir,  Chem. 
Abs.  x,  1825. 

fK2TaF7  is  soluble  in  151-157  parts  of  cold  water.  2KF-NbOF3+H2O  is 
soluble  in  12-13  parts  of  cold  water. 


124  THE  RARER  ELEMENTS. 

in  a  lead  or  platinum  dish  a,  solution  of  potassium  and 
niobium  oxyfluoride,  add  strong  sulphuric  acid,  and  heat 
until  all  the  hydrofluoric  acid  is  expelled  and  a  solution  is 
obtained.  Cool  the  solution,  dilute  with  water,  and  boil. 
Niobic  acid,  (Nb2Os),  is  precipitated.  Filter,  and  test 
the  filtrate  with  ammonium  hydroxide. 

(6)  Repeat  the  experiment,  using  a  solution  of  potas- 
sium and  tantalum  fluoride  instead  of  the  niobium  salt. 

(c)  Test  the  action  of  alkali  hydroxides  or  carbonates 
in  excess  upon  solutions  of  niobium  and  tantalum  obtained 
in  (a)  and  (6). 

(d)  Try  the  action  of  the  common  acids  upon  freshly 
precipitated  niobic  and  tantalic  acids.     Note  that  hydrogen 
dioxide  aids  the  solvent  action. 

Experiment  3.  Effect  of  fusion  with  sodium  or  potas- 
sium hydroxide  upon  niobic  and  tantalic  acids,  (a)  Melt 
a  gram  of  sodium  or  potassium  hydroxide  in  a  hard  glass 
tube,  add  a  small  quantity  of  dry  niobic  acid,  and  heat 
again.  Note  that  the  fused  mass  is  soluble  in  water. 

(b)  Repeat    the    experiment,    using    dry   tantalic    acid 
instead  of  niobic. 

(c)  Acidify  with  the  common  acids  portions  of  the  solu- 
tions obtained  in  (a)  and  (6). 

(d)  Try  the  effect  of  carbon  dioxide  upon  these  solutions. 

Experiment  4.  Tests  for  niobium,  (a)  To  separate  por- 
tions of  dry  niobic  oxide  (or  acid)  add  a  few  drops  of  strong 
sulphuric  acid,  and  treat  with  tannic  acid,  pyrogallic 
acid,  and  morphia,  respectively.  Note  the  brown  color. 

(b)  Repeat  the  experiment,  using  tantalic  oxide  instead 
of  niobic.  Note  the  absence  of  color. 

(c}  Try  the  action  of  metallic  zinc  upon  an  acid  solution 
containing  niobium.  Note  the  color.  Filter,  and  add  a 
solution  of  mercuric  chloride.  Note  the  precipitate. 

Experiment  5.  Negative  tests  of  niobium  and  tantalum. 
Note  that  hydrogen  sulphide  gives  no  precipitate,  and 
that  hydrogen  peroxide  gives  no  yellow  color  with  acid 
solutions  containing  niobium  or  tantalum. 


CHAPTER   VIII. 

MOLYBDENUM,  Mo,   96. 

Discovery.  The  name  Molybdena,  derived  from 
lead,  was  originally  applied  to  a  variety  of  substances  con- 
taining lead.  Later  the  term  was  used  to  designate  only 
graphite  and  a  mineral  sulphide  of  molybdenum  which  is 
very  similar  in  appearance  to  graphite,  and  which  was 
confused  with  it.  In  1 778  Scheele,  in  his  treatise  on  molyb- 
dena  (Kong.  Vet.  Acad.  Handl.  (1778),  247),  showed  that 
it  differs  from  plumbago,  or  graphite,  in  that  on  being 
heated  with  nitric  acid  it  yields  a  peculiar  white  earth, 
which  he  proved  to  be  an  acid-forming  oxide.  This  he  called 
' '  acidum  molybdenas, ' '  and  he  supposed  the  mineral  to  be 
a  compound  of  this  oxide  with  sulphur.  In  1790  Hjelm 
(ibid.  (1790),  50;  Ann.  de  Chim.  iv,  17)  isolated  the  ele- 
ment. 

Occurrence.      Molybdenum    occurs    in     combination    in 
minerals    which    are    somewhat    widely    diffused,    though 
found  in  small  amounts: 
Molybdic  ocher  or  Contains  Mo03 

Molybdite,  Fe2O3-3Mo03-  7§H2O 57~59% 

Powellite,  Ca(Mo,W)04 58-59% 

Wulfenite,  PbMoO4 3  7-40% 

Belonesite,  MgMoO4? 78-79% 

Pateraite,  CoMoO4? . . . . » 30% 

Scheelite,  CaWO4 traces-8% 

Koechlinite,  Bi2O3  •  MoO3 23-24% 

Molybdenite,  MoS2 6o%Mo 

Ilsemannite,  MoO2  •  4MoO3 68%Mo 

125 


126  THE  RARER   ELEMENTS 

Extraction.  Molybdenum  salts  are  usually  obtained 
from  molybdenite,  the  most  abundant  ore,  though  some- 
times from  other  minerals.  The  following  processes  will 
illustrate  the  methods  employed. 

(1)  From   molybdenite.     The    mineral   is   roasted   until 
sulphur  dioxide  is  no  longer  given  off  and  the  residue  is 
yellow  when  hot  and  white  when  cold.     This  residue  is 
dissolved  in  dilute  ammonium  hydroxide,  and  the  solution 
is    evaporated    to    crystallization.     Heat    drives    off    the 
ammonia    from    the   crystals  and  leaves  the   trioxide   of 
molybdenum. 

(2)  From   molybdenite.     The    mineral   is    treated   with 
nitric  acid  (vid.  Experiment  i). 

(3)  From  wulfenite.     The  mineral  is  fused  with  potas- 
sium poly  sulphide.     Upon  extraction  with  water  the  lead 
remains  insoluble,  as  the  sulphide,  and  the  molybdenum 
goes  into  solution  as  the  sulpho  salt.     The  nitrate  is  acidi- 
fied with  sulphuric  acid,  and  the  sulphide  of  molybdenum 
is  precipitated   (Wittstein). 

The  Element.  A.  Preparation.  Elementary  molybde- 
num may  be  prepared  (i)  by  passing  dry  hydrogen  over 
either  the  trioxide  or  the  ammonium  salt  at  red  heat; 
(2)  by  reducing  the  chlorides  \uthhydrogen;  (3)  by  heat- 
ing the  oxLe  (MoOs)  \\ith  "  misch -metal  ";  (4)  by  heat- 
ing the  oxide  (MoO^)  with  aluminum  (Goldschmidt  pro- 
cess) . 

B.  Properties.  Molybdenum  is  a  gray  metallic  powder, 
which  is  unchanged  in  the  air  at  ordinary  temperatures,  but 
which,  when  heated,  passes  gradually  into  the  trioxide. 
It  is  insoluble*  in  hydrochloric,  hydrofluoric,  and  dilute 
sulphuric  acids,  but  soluble  in  nitric  and  concentrated 
sulphuric  acids,  in  aqua  regia,  in  chlorine  water,  in  melted 
potassium  hydroxide,  and  in  melted  potassium  nitrate.  Its 
specific  gravity  is  8.6.  Its  melting-point  is  2550°  C. 

*  For  solubilities  vid.  Ruder,  Jour.  Amer.  Chem.  Soc.  xxxiv,  387. 


MOLYBDENUM.  I2j 

Compounds.*    A.  Typical  forms.    The  following  are  typ- 
ical compounds  of  molybdenum: 

Oxides  ......  MoO       Mo2Os    MoOz      MojOu   Mo3O8  MoO8 

Chlorides!..  Mod,     MoCl3     MoCl4  MoCI8 

Oxycblorides.  MoOCL, 

MoO,cf, 

Bromides  ____  MoBr8     MoBr3     MoBr4 

Oxybromide.  .  MoO2Br, 

Oxyiodide  ----  MoO^I 

Fluoride  .....  MoF, 

Oxyfluorides.  MoOF3.2KF 

+  H20 

Mo02F2-KF 


Carbides  .....  Mo,C  MoC 

Silicide  ......  MoSi 

Sulphides  ____  MoS2  MoS,;  MoS4 

i 
Sulpho  salt.  .  .  R2MoS4 

Molybdates,  many  salts  of  the  type  R,MoO4,  as  K2MoO4;  CaMoO,;  ZnMoO4; 
Ag2MoO4;  etc.  The  formula  for  ammonium  molybdate  is  given  as 
(NH4)6Mo7O24+4H2O.  Barbieri  has  formed  a  series  of  molybdates  of  the  rare 

earths  of  the  type  (  NH4)3RMo7O24+  1  2H2O,where  R  =  Ce,  La,  Nd,  Pr,  or  Sm. 

Molybdenum  trioxide  combines  with  phosphoric  pent- 
oxide  in  the  following  proportions:  P2O5:  MoO3:  :i  :  24, 
1:22,  1:20,  1:18,  1:16,  1:15,  1:5,  as  2K2HPO4-24MoO3  + 
3H2O;  2(NH4)3PO4-i6MoO3+i4H2O;  etc.  It  combines 
with  arsenic  pentoxide  as  follows  :  As2O5  :  MoO3  :  :  i  :  20, 
1:18,  1:16,  1:6,  1:2,  as  As2O5'2oMoO3  +  27H20; 
ioNH3.As2O5-i6MoO3  +  i4H2O;  etc. 

B.  Characteristics.     The  molybdenum    compounds    are 

*  See  also  Bailhache,  Compt.  rend,  cxxxv,  862;  Mylius,  Ber.  Dtsch.  chem. 
Ges.  xxxvi,  638;  Rosenheim,  Zeitsch.  anorg.  Chem.  xxxiv,  427;  XLVI,  311; 
XLTX,  148;  L,  320;  LIV,  97;  LXXIX,  292;  Lxxxiv,  217;  xci,  75;  Grossmann, 
Zeitsch.  anorg.  Chem.  XLI,  43;  Zeitsch.  phys.  Chem.  LVI,  577;  LIV,  40;  Weinland, 
Zeitsch.  anorg.  Chem.  XLIV,  81;  Sand,  Ber.  Dtsch.  chem.  Ges.  xxxvin,  3384;  XL, 
4504;  Copaux,  Ann.  chim.  phys.  [8]  vn,  118;  Bull.  Soc.  franc.  Mineral,  xxx, 
292  (Oct.  1907),  or  Chem.Zentr.  (1908)  i,  711;  Lancien,  Bull.  d.  Sciences  Pharmacol. 
xv,  132,  or  Chem.  Zentr.  (1908)  i,  1763;  Ruff,  Ber.  Dtsch.  chem.  Ges.  XL,  2926; 
Hilpert,  Ber.  Dtsch.  chem.  Ges.  XLVI,  1669. 

t  Michael  and  Murphy,  Amer.  Chem.  Jour,  xuv,  365, 


128  THE  RARER  ELEMENTS. 

known  in  various  conditions  of  oxidation  (vid.  Typical 
Forms),  of  which  the  highest,  (MoOs),  is  the  most  stable  and 
comprises  the  largest  number  of  salts.  The  trioxide  is 
white  to  pale  yellow,  and  dissolves  in  potassium,  sodium, 
and  ammonium  hydroxides,  forming  the  molybdates. 
The  alkali  molybdates  are  the  only  soluble  molybdates. 
When  strong  reducing  agents,  such  as  zinc  and  hydro- 
chloric acid,  act  upon  acid  solutions  of  molybdates,  the 
reduction  is  said  to  go  as  far  as  the  oxide  Mo5O7,  the  solu- 
tion passing  through  the  colors  of  the  various  oxides, 
violet,  blue,  and  black.  The  oxide  Mo5O7,  however,  is 
Very  sensitive  to  oxidation,  for  it  is  changed  in  the  air  to 
the  sesquioxide  (Mo2O3)  as  soon  as  the  reducing  action  has 
ceased.  Acid  solutions  of  the  lower  oxides  give,  on  treatment 
with  the  alkali  hydroxides,  the  corresponding  hydroxides  of 
molybdenum,  Mo2O3  •  3H2O ;  MoO2  •  *H2O ;  etc.  The  sulphide 
(MoS3)  is  obtained  by  treating  a  molybdate  with  ammonium 
sulphide  and  acidifying.  Its  color  is  reddish  brown. 

Estimation.*  A.  Gravimetric.  Molybdenum  is  generally 
weighed  as  the  oxide  (MoO3),  obtained  (i)  by  ignition  of 
ammonium  molybdate;  (2)  by  precipitation  of  mercury 
molybdate  and  ignition;  or  (3)  by  precipitation  of  the 
sulphide  and  conversion  into  the  oxide  by  treatment  with 
nitric  acid. 

B.  Volumetric.  Soluble  molybdates  may  be  reduced 
in  acid  solution  (i)  by  boiling  with  potassium  iodide, 
(a)  The  iodine  thus  liberated  may  be  passed  into  potassium 
iodide  and  estimated  by  standard  thiosulphate,  the  amount 
of  molybdenum  present  being  calculated  from  the  equation 
2MoO3  +  2HI-Mo2O5  +  I2  +  H2O;  or,  (6)  after  the  iodine  has 
been  removed  by  boiling,  the  residual  solution  may  be 
rendered  alkaline  by  potassium  bicarbonate  and  reoxidized 

*  For  the  estimation  in  ores,  see  Low's  Technical  Methods  of  Ore  Analysis; 
Blair,  Jour.  Amer.  Chem.  Soc.  xxx,  1229. 


MOLYBDENUM.  129 

by  standard  iodine  solution  or  potassium  permanganate 
(Mauro  and  Danesi,  Zeitsch.  anal.  Chem.  xx,  507;  Fried- 
heim  and  Euler,  Ber.  Dtsch.  chem.  Ges.  xxvm,  2066; 
Gooch  and  Fairbanks,  Amer.  Jour.  Sci.  [4]  n,  156;  Gooch 
and  Pulman,  Amer.  Jour.  Sci.  [4]  xn,  449) ;  (2)  by  passing 
the  solution  over  zinc  in  a  Jones  reductor  into  a  flask 
charged  with  a  ferric  salt.  The  molybdic  acid,  reduced  to 
the  sesquioxide  (Mo2O3)  in  the  reductor  is  reoxidized  by 
the  ferric  salt,  and  the  ferrous  salt  formed  is  titrated  by 
permanganate  (Randall,  Amer.  Jour.  Sci.  xxiv  (1907),  313). 
See  also  under  Vanadium  a  volumetric  process  for  the 
estimation  of  vanadium  and  molybdenum  in  the  presence 
of  each  other,  page  112. 

Separation.  The  general  methods  for  the  separation 
of  molybdenum  from  the  metals*  and  alkali  earths  are  the 
same  as  those  described  under  Vanadium. 

From  arsenic  and  phosphorus,  when  present  as  arsenic 
and  phosphoric  acids,  molybdenum  may  be  separated  by 
magnesium  chloride  mixture  in  ammoniacal  solution, 
ammonium-magnesium  arseniate  and  phosphate  being 
precipitated  (Gibbs,  Amer.  Chem.  Jour,  vn,  317;  Gooch, 
Amer.  Chem.  Jour,  i,  412). 

For  the  separation  from  vanadium,  vid.  Vanadium. 

From  tungsten  molybdenum  may  be  separated  (i)  by 
the  action  of  warm  sulphuric  acid  of  specific  gravity  1.37 
upon  the  oxides  (MoO3  and  WO3),  molybdic  acid  dissolv- 
ing (Ruegenberg  and  Smith,  Jour.  Amer.  Chem.  Soc. 
xxii,  772);  (2)  by  heating  the  oxides  with  hydrochloric- 
acid  gas  at  25o°-27o°  C.,  the  molybdenum  compound 
(MoO3-2HCl)  being  volatilized  (Pechard,  Compt.  rend, 
cxiv,  173;  Debray,  ibid.  XLVI,  noi);  (3)  by  precipitation 
of  tungstic  acid  by  means  of  stannous  chloride  (Marbaker, 
Jour.  Amer.  Chem.  Soc.  xxxvn,  86). 

*  Molybdenum  and  tungsten  may  be  separated  electrolytically  from  copper, 
lead,  and  mercury  (McCay  and  Furman,  Jour.  Amer.  Chem.  Soc.  xxxvm,  640). 


130  THE  R4RER   ELEMENTS. 


EXPERIMENTAL  WORK   ON   MOLYBDENUM. 

Experiment  i.  Extraction  of  molybdenum  salts  from 
molybdenite,  (MoS2).  'Heat  5  grm.  of  the  finely  powdered 
mineral  with  nitric  acid  until  the  dark  color  has  disap- 
peared. Evaporate  to  dryness,  wash  the  residue  in  warm 
dilute  nitric  acid,  then  in  water,  and  dissolve  it  in  am- 
monium hydroxide.  Filter,  and  evaporate  the  filtrate  to 
a  small  volume.  Ammonium  molybdate  crystallizes  out, 
which  may  be  converted  into  the  trioxide  by  careful 
ignition. 

Experiment  2.  Precipitation  of  the  sulphides  of  molyb- 
denum, (MoS2;  MoS3).  (a)  Through  a  solution  of  am- 
monium molybdate  acidified  with  hydrochloric  acid  pass 
hydrogen  sulphide.  Note  the  gradual  change  of  color 
of  the  solution,  from  red-brown  to  blue,  and  the  partial 
precipitation  of  the  sulphide  MoS2. 

(6)  To  a  solution  of  ammonium  molybdate  add  am- 
monium sulphide,  or  pass  hydrogen  sulphide  through  an 
alkaline  solution  of  a  molybdate.  Note  the  yellow-brown 
color  ((NH4)2MoS4,  typical).  Acidify  the  solution  and 
note  the  brown  precipitate  (MoS3). 

Experiment  3.  Precipitation  of  ammonium  phospho- 
molybdate  (3(NH4)2O-P2O5-24(MoO3)  +  2H2O).  To  a  solu- 
tion of  ammonium  molybdate  acidified  with  nitric  acid 
add  a  drop  of  a  solution  of  sodium  phosphate,  and  warm 
gently.  Note  the  yellow  precipitate. 

Experiment  4.  Precipitation  of  the  molybdates  of 
silver,  lead,  and  barium,  (Ag2MoO4,  PbMoO4,  and  BaMoO4, 
typical).  To  separate  solutions  of  ammonium  molybdate, 
neutral  or  faintly  acid  with  acetic  acid,  add  solutions  of 
silver  nitrate,  lead  acetate,  and  barium  chloride  respec- 
tively. Note  the  solvent  action  of  nitric  acid  upon  tho 
precipitates. 

Experiment    5.     Reduction    of   molybdic    acid,    (MoOa). 


TUNGSTEN.  131 

(a)  Put  a  piece  of  metallic  zinc  into  a  solution  of  ammo- 
nium molybdate  and  add  hydrochloric  acid  until  the  action 
starts.  Note  the  change  in  color  of  the  solution  as  the 
reduction  proceeds  (reddish  yellow,  violet,  bluish,  black). 
To  a  few  drops  of  the  solution  after  reduction  add  potas- 
sium or  sodium  hydroxide.  Note  the  dark-brown  pre- 
cipitate of  the  lower  hydroxides  of  molybdenum  (Mo2(OH)6> 
etc.)  mixed  with  the  hydroxide  of  zinc. 

(6)  Try  the  reducing  action  of  stannous  chloride  upon 
a  molybdate  in  solution.  Try  also  the  action  of  hydrazine 
sulphate. 

(c)  To  a  dilute  solution  of  a  molybdate  which  has  been 
treated  with  zinc  and  hydrochloric  acid,  add  some  potas- 
sium sulphocyanide  in  solution.     Note  the  red  color.     Try 
the  effect  of  adding  ether  and  shaking. 

(d)  To  a  few  drops  of  a  solution  of  a  molybdenum  com- 
pound add  a  little  strong  sulphuric  acid,   and  evaporate 
nearly    to    dryness   in    a   porcelain    dish.     Note    the    blue 
color. 

Experiment  6.  Formation  of  a  permolybdatc.  To  a  solu- 
tion of  a  molybdenum  compound  add  ammonium  hydroxide 
and  hydrogen  dioxide.  Note  the  red  color  of  the  ammonium 
permolybdate. 

Experiment  7.  Formation  of  molybdenum  ferrocyanide. 
To  a  solution  of  a  molybdate  acidified  with  hydrochloric 
acid  add  a  solution  of  potassium  ferrocyanide.  Note  the 
brown  precipitate  and  its  solubility  in  ammonium  hydroxide. 

TUNGSTEN,  W.     184. 

Discovery.  The  minerals  scheelite,  formerly  called 
tungsten  (i.e.  "heavy  stone"),  and  wolframite  have  long 
been  known,  but  until  about  the  middle  of  the  eighteenth 
century  they  were  regarded  as  tin  ores.  In  1781  Scheele 
(Kong.  Vet.  Acad.  Handl.  (1781),  89)  demonstrated  that 
scheelite  contained  a  peculiar  acid  which  he  named  Tung- 


132  THE  RARER  ELEMENTS. 

•stic  acid.     Two  years  later  the  brothers  D'Elhujar  showed 
the  presence  of  the  same  acid  in  wolframite. 

Occurrence.      Tungsten  is  found    combined  in  minerals 
which  are  often  associated  with  tin  ores: 

Contains 
WOS. 

Wolframite,  (Fe,Mn)WO4 74-?8% 

Scheelite,  CaWO4 71-80% 

Hubnerite,  MnWO4 73-77% 

Cuprotungstite,  CuWO4 56~57% 

Cuproscheelite,  (Ca,Cu)WO4 76-80% 

Powellite,  Ca(Mo,W)O4 10-11% 

Stolzite,  PbWO 51  circa 

Raspite,  PbWO4 49 

Reinite,  FeWO4 75~76% 

Ferberite,  FeWO4 69-70% 

Ferritungstite,  Fe2O3-WO3-6H20 42-45% 

Yttrotantalite,  complex  niobate-tantalate 2-  4% 

Tungstite,  WOs 100  circa 

Meymacite,  hydrated  WOs 7I-75% 

Tungstenite,  WS2 44~45%  W 

Extraction.  *    Tungstic  acid  is  usually  extracted  from  wol- 
framite. Any  of  the  processes  here  indicated  may  be  followed : 

(1)  5  parts  of  the  mineral  are  fused  with  8.5  parts  of 
dry  sodium  carbonate  and   1.5   parts  of  sodium  nitrate. 
On  treatment  cf  the  fused  mass  with  water,  sodium  tung- 
state  is  dissolved,  and  after  filtration  tungstic  acid  is  pre- 
cipitated by  hydrochloric  acid. 

(2)  The  mineral  is  fused  with  an  equal  weight  of  cal- 
cium carbonate  and  one-half  of  its  weight  of  sodium  chlor- 
ide, and  the  melt  is  treated   with   hot   water   containing 
liydrochloric  and  nitric  acids.     The  tungstic  acid  remains 
undissolved. 

*  See  also  an  interesting  discussion  of  the  treatment  of  tungsten  ores,  etc., 
.by  Van  Wegenen,  The  Chemical  Engineer,  Vol.  iv,  217-232  and  284-297. 


TUNGSTEN.  133 

(3)  The  mineral  is  decomposed  by  hydrochloric  acid 
(wd.  Experiment  i). 

The  Element.  A.  Preparation.*  Elementary  tungsten 
may  be  obtained  (i)  by  heating  the  acid  in  the  presence 
of  hydrogen;  (2)  by  heating  the  chloride  (WC16)  in  the 
presence  of  hydrogen;  (3)  by  heating  the  acid  with  carbon; 
(4)  by  heating  the  nitride;  (5)  by  passing  an  electric  current 
in  vacua  through  filaments  of  an  amalgam  of  tungsten, 
cadmium,  and  mercury,  the  cadmium  and  mercury  being 
expelled  and  the  tungsten  left;  (6)  by  heating  the  acid 
with  metallic  zinc  (Weiss). 

B.  Properties*  Tungsten  is  a  very  hard  powder,  rang- 
ing in  color  from  gray  to  brownish  black,  resembling  some- 
times tin,  sometimes  iron.  Although  unchanged  in  the  air 
at  ordinary  temperatures,  when  heated  in  finely  divided 
condition  it  ignites  and  burns  to  the  oxide  (WOs).  Its 
melting-point  is  variously  given  as  2650°  (Ruff),  2850° 
(Weiss),  2900°  (v.  Wartenburg).f  It  is  slowly  attacked 
when  heated  with  sulphuric  or  nitric  acid;  and  readily 
attacked  by  a  mixture  of  nitric  and  hydrofluoric  acids,  J 
forming  WFe  or  WOF4,  and  by  fusion  with  alkalies  and  salt- 
peter. It  is  acted  upon  also  by  dry  chlorine  at  high  tem- 
peratures. It  forms  alloys  with  other  metals.  The  specific 
gravity  of  tungsten  is  from  19.3  to  20.2. 

Compounds.  §  A.  Typical  forms.  The  following  com- 
pounds of  tungsten  may  be  considered  typical: 

Oxides  II W02  WO3 

Chlorides WC12     WC14  WC15  WC16 

Oxychlorides WOC14 

WO2C!2 
Bromides WBr2 WBr5 

*  See  Weiss,  Zeitsch.  anorg.  Chem.  LXV,  279. 

t  U.  S.  Bureau  of  Standards  gives  3400°  C. 
Jeffries,  Eng.  and  Min.  Jour.  (1918)  227,  gives  3350°  C. 

t  For  solubilities  vid.  Ruder,  Jour.  Amer.  Chem.  Soc.  xxxrv,  387. 

§  See  also  Rosenheim,  Zeitsch.  anorg.  Chem.  LIV,  97. 

II  Some  authorities  give  three  oxides  between  the  dioxide  and  the  trioxide,  viz., 
W2O5,  WSO8, 


134  THE  RARER  ELEMENTS. 

Oxybromides WOBr4 

WO2Br, 

Iodide WI« 

Fluoride WF8 

Double  fluorides. .  KF-W02F+H20    ZnF2-WO2F2+ioH20; 

etc. 

Carbide WC 

Cyanides  * K4W(CN)8;K3W(CN)8 

Boridef WB2 

Silicide WSi, 

Sulphides WS2  WS, 

Sulpho  salts R2WS4 

R2WS20, 
R2WSO3 

Tungstates,  many  salts  of  the  types  R2WO4  (normal) 

R2W4O13  (meta) 
R.W7024  (para) 

Tungstic  trioxide  (acid)  combines  with  phosphoric 
pentoxide,  arsenic  pentoxide,  and  silicon  dioxide  in  the 
following  proportions: 

P2O5:  WO3: :  i :  22,  i :  21,  i :  20,  i :  16,  i :  12,  i :  7. 
As2O5:WO3::i:i6,  i :  6,  i :  3. 
SiO2:  WO3:  :  i:  12,  i:  10. 

B.  Characteristics.  The  compounds  of  tungsten  are 
very  similar  to  those  of  molybdenum,  and  are  known 
in  several  conditions  of  oxidation  (vid.  Typical  Forms),  of 
which  the  highest  is  the  most  stable.  The  trioxide,  (WO3), 
united  with  the  bases,  forms  the  largest  number  of  salt" 
the  tungstates.  The  alkali  tungstates  are  the  chief  soluble 
salts.  When  acted  upon  by  reducing  agents,  tungstic 
acid  or  trioxide  may  be  reduced  to  the  dioxide,  (WO2), 
the  solution  becoming  blue,  then  brown.  When  the  solu- 
tion of  a  tungstate  is  acidified,  tungstic  acid  is  precip- 
itated. Tungstic  sulphide,  (WS3),  is  obtained  under  the 
same  conditions  as  molybdenum  sulphide,  and  is  brown. 

*  Olsson,  Ztschr.  anorg.  Chem.  Lxxxvm,  49;    Rosenheim,  Ber.  Dtsch.  chem. 
Ges.  XLVH,  392. 

f  Wedekind,  Ber.  Dtsch.  chem.  Ges.  xivi,  1198. 


EXPERIMENTAL   WORK  ON    TUNGSTEN.  135 

It   dissolves   in    ammonium    sulphide,  forming    a    sulpha 
salt. 

Estimation.*  Tungsten  is  ordinarily  weighed  as  the  oxide 
(WO3),  obtained  (i)  by  igniting  ammonium  tungstate;  (2) 
by  decomposing  the  alkali  tungstates  with  nitric  acid, 
evaporating  to  dryness,  and  extracting  with  water, — tung- 
stic  acid  remaining  undissolved;  (3)  by  precipitating  mer- 
cury tungstate  and  driving  off  the  mercury  by  means  of 
heat,  leaving  the  acid  or  oxide;  (4)  by  boiling  fused  lead 
tungstate  with  strong  hydrochloric  acid, — tungstic  acid 
being  precipitated  (Brearley,  Chem.  News  LXXIX,  64). 

Separation.  Tungsten  may  be  separated  from  the  me- 
tallic bases  and  many  other  elements  by  the  following 
process:  fusion  with  an  alkali  carbonate,  extraction  of  the 
alkali  tungstate  with  water,  acidification  with  nitric  acid, 
evaporation  to  dryness,  and  extraction  with  water, — tung- 
stic acid  remaining  undissolved. 

For  the  separation  of  tungsten  from  molybdenum  and 
vanadium,  see  those  elements.  From  arsenic  and  phos- 
phorus tungsten  is  separated  by  magnesium  mixture 
(Gooch,  Amer.  Chem.  Jour,  i,  412;  Gibbs,  Amer.  Chem. 
Jour,  vii,  337). 

From  tin  the  separation  may  be  accomplished  (i)  by 
ignition  with  ammonium  chloride,  tin  chloride  being  vola- 
tilized (Rammelsberg) ;  (2)  by  fusion  with  potassium  cyanide, 
the  tin  being  reduced  to  the  metal  and  the  tungsten  being 
converted  into  a  soluble  tungstate  (Talbot). 


EXPERIMENTAL  WORK  ON  TUNGSTEN. 
Experiment    i.      Extraction  of  tungstic  acid   from  wol- 
framite ((Fe,Mn)WO4).     Treat  5  grm.  of  the  finely  powdered 
mineral  with  about  10  cm.3  of  a  mixture  of  equal  parts  of 
hydrochloric  acid  and  water,  and  boil  as  long  as  any  action 

*  For  the  estimation  in  ores  see  Low's  Technical  Methods  of  Ore  Analysis. 


136  THE  RARER   ELEMENTS. 

seems  to  take  place.  Decant  the  solution,  add  to  the 
residue  about  10  cm.3  of  a  mixture  of  nitric  and  hydro- 
chloric acids  (aqua  regia),  and  warm.  Add  more  acid  if 
necessary,  and  continue  this  treatment  until  the  residue  is 
yellow ;  filter,  and  wash  with  dilute  hydrochloric  acid  and 
then  with  water.  Warm  the  yellow  mass  with  ammonium 
hydroxide  as  long  as  any  solvent  action  is  observed,  and 
filter.  Evaporate  the  filtrate  to  dryness  and  ignite  the 
ammonium  tungstate  to  obtain  tungstic  acid. 

Experiment  2 .  Formation  of  sodium  tungstate  and  meta- 
tungstate  (Na2WO4  and  Na2W4Oi3,  typical),  (a)  Dissolve  a 
little  tungstic  acid  in  a  solution  of  sodium  carbonate. 

(6)  Dissolve  a  little  tungstic  acid  in  a  solution  of  sodium 
tungstate. 

Experiment  3.  Precipitation  of  tungstic  sulphide  (WSs), 
and  formation  of  the  sulpho  salt  ((NH4)2WS4).  (a)  To  a 
solution  of  sodium  or  ammonium  tungstate  add  ammonium 
sulphide,  and  acidify  with  hydrochloric  acid. 

(6)  Try  the  action  of  hydrogen  sulphide  upon  a  soluble 
tungstate. 

(c)  Try  the  action  of  ammonium  sulphide  upon  tungstic 
sulphide. 

Experiment  4.  Precipitation  of  tungstic  acid  (WO3). 
Acidify  a  concentrated  .oluti  n  cf  a  tungstate  with  hydro- 
chloric or  nitric  acid  and  boil.  Try  the  action  of  nitric 
and  hydrochloric  acids  upon  a  xungstate  in  the  presence  of 
tartaric  acid. 

Experiment  5.     Precipitation  of  barium,  lead,  and  silver 

tungstates  (R2WO4,  typical).  To  separate  portions  of  a 
solution  of  sodium  tungstate  acidified  with  acetic  acid  add 
solutions  of  barium,  lead,  and  silver  salts  respectively. 

Experiment  6.  Reduction  of  tungstic  acid,  (a)  To  a 
solution  of  a  tungstate  (e.g.,  sodium  tungstate)  add  a  solu- 
tion of  stannous  chloride.  Acidify  with  hydrochloric  acid 
and  warm  gently.  (6)  To  a  solution  of  a  tungstate  add  zinc 
and  hydrochloric  acid  and  warm  gently. 


URANIUM. 


137 


Experiment  7.  Salt  of  phosphorus  bead  tests.  Make  a 
bead  of  microcosmic  salt,  and  heat  it  in  the  oxidizing  and 
reducing  flames  with  a  small  particle  of  tungstic  acid. 
Try  the  effect  of  a  small  amount  of  ferrous  sulphate  upon 
the  bead  heated  in  the  reducing  flame. 


URANIUM,*  U,  238.2. 

Discovery.  Klaproth,  in  the  year  1789,  discovered  that 
the  mineral  pitch-blende,  supposed  to  be  an  ore  of  zinc, 
iron,  or  tungsten,  contained  a  "half-metallic  substance" 
differing  in  its  reactions  from  all  three  (Crell  Annal.  (1789) 
n,  387).  This  he  named  Uranium  in  honor  of  Herschel's 
discovery  of  the  planet  Uranus  in  1781.  The  body  that 
Klaproth  obtained  was  really  an  oxide  of  uranium,  as 
Peligot  showed  in  1842,  when  he  succeeded  in  isolating 
the  metal  (Ann.  de  Chim.  (1842)  v,  5). 

Occurrence.  Uranium  is  found  combined  in  a  few  min- 
erals, most  of  them  rare.  Pitch-blende  is  the  most  abun- 
dant source. 

Uraninite  (pitch-blende),  UO3 •  UO2 •  PbO •  N,  etc.,  contains  75-85%  (UO2+U03) 


Broggerite,  vid.  Uraninite, 

76-79% 

Cleveite,  vid.  Uraninite, 

66%,           " 

Nivenite,  vid.  Uraninite, 

67% 

Thorianite,  ThO2-U3O8, 

<        12-25%  U 

Gummite,  (Pb,Ca)U3SiOi2-  6H2O?, 

'        6i-75%U03 

Thorogummite,  UO3  •  3ThO2  •  3Si02  •  6H2O, 

'        22-23%    " 

Pilbarite,  PbO  •  UO3  •  ThO2  •  2SiO2  •  2H2O+  2H,O, 

'        27.09%    " 

Mackintoshite,  UO2  •  3ThO2  •  sSiO2  •  3H2O, 

'            21-22%  U02 

Uranophane,  CaO  •  2UO3  •  2Si02  •  6H>O, 

'       53-67%  UQ, 

Naegite,f  silicate, 

<        28-29%  U02 

Uranosphaerite,  (BiO)2U2O7  •  3H20, 

'        50-51%  U03 

Walpurgite,  Bi10(U02)3(OH)24(As04)4, 

'            20-21%     " 

Carnotitc,  K2O  •  2UO3  •  V2O5  •  8H2O 

'     62-65%  " 

Torbernile,  Cu(UO2)2P2Os-SH2O, 

'    57-62%  " 

Zeunerite,  Cu(UO2)2As2Os  •  8H2O, 

'    55-56%  " 

*  For  a  discussion  of  radioactive  properties,  see  Chapter  III. 
f  A  Japanese  mineral,  Chem.  Zentr.  (1905)  I,  763. 


'38 


THE  RARER  ELEMENTS. 


Autunite,  Ca(UO2)2P2O8-8H2O, 
Uranospinite,  Ca(UO2)2As2O8-8H2O 
Uranocircite,  Ba(UO2)2P2O8-8H2O, 
Johannite,  sulphate,  formula  doubtful, 
Uranopilite,  CaO  •  8UO3  •  2SO3  •  2sHA 
Uranochalcite,  vid.  Uranopilite, 
Zippeite,  vid.  Uranopilite, 
Voglianite,  vid.  Uranopilite, 
Uraconite,  vid.  Uranopilite, 
Thorite,  ThSiO4, 

Phosphuranylite,  (UO2)3P2O8  •  6H20, 
Trogerite,  (UO2)3As2O8-i2H2O, 
Rutherfordite,  UO2CO3, 

Uranothallite,  2CaCO3  •  U(C03)2 •  ioH20, 
Liebigite,  CaC03 •  (UO2)CO3 •  2oH20, 
Voglite,  complex  carbonate, 

Hatchettolite,  R(Nb,Ta)2O6-H20, 

in 

Fergusonite,  R(Nb,Ta)O4, 
Sipylite,  complex  niobate, 

Samarskite,  R3R2(Nb,Ta)602i, 
Nohlite,  vid.  Samarskite, 
Vetinghofite,  vid.  Samarskite, 
Ainnerodite,  complex, 

Hiehnite,  complex, 

in  in 

Euxenite,  R(NbO3)3 •  R2(Ti03)3 •  |H2O, 


Polycrase,  R(NbO3)3 •  2R(TiO3)3 •  3H2O, 
Yttrocrasite,  complex, 
Btomstrandite,  tantalo-niobate, 
Xenotime,  YPO4, 


contains  55-62%  UO| 
"        59-6o%  " 
"        56-57%  "j  ' 
"       67-68%  " 
77-78%   " 

36%  U304 
13-14%    " 

12%      " 
66-71%      " 

1-10%  UO3 
72-77%    " 
63-64%    " 
80-84%    " 

35-37%  UOs 

36-38%  U03 
37%  UOz 

15-16%  UO, 
o-  8%  UOZ 
3-  4%  " 

10-13%  U03 


14%  UO 

9%  U203  i 

"«     16-17%  UOz 

o-  5%   " 

5-12%  " 

1-19%   " 
2-  3%   " 
23%  UO 
4%  U03 

Extraction.     Uranium  salts  may  be  extracted  from  pitch- 
blende as  follows : 

(1)  The  mineral  is  decomposed  with  nitric  acid,   the 
acid  solution  is  evaporated  to  dryness,   and  the  mass  is 
extracted  with  water.     The  residue,  which  consists  largely 
of  lead  sulphate,  iron  arseniate,  and  iron  oxide,  is  filtered 
off,  and  on  evaporation  of  the  solution  impure  nitrate  of 
uranium  crystallizes  out,  which  may  be  purified  by  re- 
crystallization  (Peligot). 

(2)  The   mineral  is   decomposed  by   aqua  regia  (vid* 
Experiment  i). 


URANIUM. 


139 


The  Element.  A.  Preparation.  Metallic  uranium  may 
be  obtained  (i)  by  heating  a  mixture  of  the  chloride  UCla 
with  sodium  and  potassium  chloride  in  a  porcelain  cru- 
cible surrounded  by  powdered  carbon  contained  in  another 
crucible  (Peligot);  (2)  by  heating  the  oxide  (U308)  with 
sugar  carbon  in  a  carbon  tube  (Moissan). 

B.  Properties.  Uranium  is  a  somewhat  malleable  white 
metal  with  much  the  appearance  of  nickel.  Heated  in 
air  or  oxygen  to  a  temperature  of  i5o°-i7o°C.  it  burns 
to  the  oxide ;  at  ordinary  temperatures  the  oxidation  takes 
place  slowly.  Uranium  dissolves  slowly  in  cold  dilute  sul- 
phuric acid,  and  more  rapidly  upon  the  application  of  heat. 
It  is  soluble  in  nitric  and  hydrochloric  acids.  It  is  attacked 
by  chlorine  at  150°  C.  and  by  bromine  at  240°  C.  The  caustic 
alkalies  have  no  apparent  action  upon  the  element.  The  spe- 
cific gravity  of  uranium  is  18.6.  Its  melting-point  is  1850°  C. 

Compounds.*  A.  Typical  forms.  The  following  are  typ- 
ical compounds  of  uranium: 


Oxides  f  .  .  .  . 
Carbonates 

.  .  .  . 

UOj 

Chlorides  .    . 

UC1, 

ucu 

UBr3 

UBr 

Iodide  
lodate 

UI4 

Fluorides 

.  .UF, 

UF. 

Sulphides.  .  .  , 

US   U2S3 

UOF, 
US, 

U3O8(U02 


UC15 
UBrs 


UF, 


U03 

U02C03-2K,C03 

U02C03-2(NH4)2CO, 

UO:C12 

U02Br2 

U02(I03), 


Sulphates UH(SO4)2    U(SO4)2-f 

4H20 

Nitrate 

Nitride U3N4 


UO2F2-XaF,  etc. 
UOS2 

uo,s 

U02S04+3 


'  U02(N03)2+6H.O 


*See  also  Giolitti,  Gazz.  chim.  ital.  xxxv  [n],  145,  151,  162,  170;  Colani, 
Ann.  Chim.  Phys.  [Sjxii,  59-144  (1907);  Mazzucchelli,  Atti  R.  Accad.  dei  Lincei, 
Roma  [5]  xvi  [n],  576;  also  Chem.  Zentr.  (1908)  I,  218;  Lancien,  Chem.  Zentr. 
(1908)  i,  1763;  Aloy,  Chem.  Zentr.  (1907)  n,  883. 

t  Other  oxides  less  well  known  than  those  given  above  are  of  the  following 
forms:  UO,  U2O»,  U3O4,  and  UO4. 


140  THE  R4RER  ELEMENTS. 

Boride. UB2 

Ferrocyanides.  . .  .  UFe(CN)8  (UO2)3K2(FeC6N8)j 

Phosphates,  ortho.  UOHPO4  (UO2)5H2(PO4)4 

pyro..  (UO)2P207  (UO2)2P2O7 

meta..  UO(PO3)2  UO2(PO3)2 

Arseniate UO2HAsO4+ 4H,Q 

Uranates,  of  types  R2UO4,  R2U2O7,  and  R4UO8. 
Peruranates,  (Na2O2)2UO4-8H2O;  (PbO)2UO4.PbUO4. 

B.  Characteristics.     Uranium  differs  from  molybdenum 
and    tungsten   in   manifesting   less    marked    acidic   quali- 
ties.     The  chief  classes  of  salts  are  the  uranyl,  in  which 
uranium    shows    its    highest    degree    of   oxidation,  corre- 
sponding to  the  oxide  UO3   (e.g.,  UO2C12),  and  the  ura- 
nous,  of  which   the  oxide  UO2   is  the   type  (e.g.,    UC14). 
The  uranyl  salts  are  the  more  stable  and  better  known. 
They  may  be  reduced  by  zinc  and  hydrochloric  acid  to. 
the  lower  condition.     The  uranous  salts  are  easily  oxidized 
to   the   higher  form.     The   uranyl   salts  are,   in  general, 
yellow,    the    uranous    greenish.     The    two    conditions    of 
oxidation  may  be  further  distinguished  by  the  following 
reactions:   the   precipitate   resulting   from   the   action   of 
ammonium  sulphide  upon  uranyl  salts  is  reddish  brown, — 
upon  uranous  salts,  light  green;  the  precipitate  resulting 
from  the  action  of  potassium  ferrocyanide  upon  uranyl 
salts  is  blood-red, — upon  uranous   salts   yellowish   green. 

Uranates  of  the  types  R2UO4  and  R2U2O7  are  formed  by 
the  combination  of  the  oxide  UO3  with  the  strong  bases. 

Estimation.*  A.  Gravimetric.  Uranium  may  be 
weighed  (i)  as  urano-uranic  oxide  (U3O8),  obtained  by 
precipitation  of  ammonium  uranate  by  means  of  ammonia,, 
and  ignition  in  air  or  oxygen;  (2)  as  urano-uranic  oxide, 
precipitated  electrolytically  by  a  current  of  0.18  ampere 
and  3  volts  at  a  temperature  of  70°  C.  (Smith  and  Wallace, 
Jour.  Amer.  Chem.  Soc.  xx,  279;  Smith  and  Kollock,  ibid. 

*  Vid.  Kern,  Jour.  Amer.  Chem.  Soc.  xxm,  685.     For  the  estimation  in  ores, 
see  Low's  Technical  Methods  of  Ore  Analysis. 


URANIUM. 


141 


xxm,  607);  (3)  as  uranous  oxide  (U02),  obtained  by  ig- 
nition of  urano-uranic  oxide  in  a  current  of  hydrogen; 
(4)  as  the  pyrophosphate  ((UO2)2P2O7),  obtained  by  pre- 
cipitation by  means  of  ammonium  phosphate  in  the  pres- 
ence of  ammDnium  acetate,  and  ignition. 

B.  Volumetric.  Uranium  may  be  estimated  volumet- 
rically  (i)  by  reduction  from  the  higher  (UO3)  to  the  lower 
(UO2)  condition  of  oxidation  by  means  of  zinc  and  sul- 
phuric acid,  and  oxidation  with  permanganate,  according 
to  the  following  formulae  (Pulman,  Amer.  Jour.  Sci.  [4] 
xvi,  229)  : 


(1)  UO2SO4+Zn  +  2H2SO4=ZnSO4-|-U(SO4 

(2)  2KMnO4-t-5U(SO4)2+2H2O  = 

2KHSO4  +2MnSO4  +H2SO4  +  5UO2SO4  ; 

(2)  by  reduction  with  titanous  sulphate  and  oxidation 
with  permanganate  (Newton  and  Hughes,  Jour.  Amer. 
Chem.  Soc.  xxxvn,  1711). 

Separation.*  From  the  metals  which  precipitate  sul- 
phides with  hydrogen  sulphide  in  acid  solution,  uranium 
may  be  separated  by  hydrogen  sulphide.  From  iron, 
nickel,  and  other  members  of  its  own  group  it  may  be 
separated  by  ammonium  sulphide  in  the  presence  of  an 
excess  of  sodium  or  ammonium  carbonate,  the  uranium 
salt  remaining  in  solution.  From  the  alkalies  and  alkali 
earths  the  separation  may  be  accomplished  by  means  of 
ammonium  sulphide  in  the  presence  of  ammonium  chloride, 
uranium  oxysulphide  being  precipitated. 

*  Vid.  Kern,  Jour.  Amer.  Chem.  Soc.  xxin,  685.     For  the  estimation  in  ores, 
see  Low's  Technical  Methods  of  Ore  Analysis. 


I42  THE  RARER  ELEMENTS. 

EXPERIMENTAL  WORK  ON  URANIUM. 

Experiment  i .  Extraction  of  uranium  salts  from  pitch' 
blende.  Warm  5  grm.  of  pulverized  pitch-blende  with 
aqua  regia  until  the  decomposition  is  complete,  and  remove 
the  excess  of  acid  by  evaporation.  Extract  with  water  and 
boil  the  solution  a  few  minutes  with  sulphurous  acid  to 
reduce  the  arsenic  acid.  When  the  liquid  is  at  about  60°  C., 
pass  hydrogen  sulphide  through  to  the  complete  precipita- 
tion of  arsenic,  copper,  lead,  bismuth,  and  tin.  Filter, 
oxidize  the  nitrate  with  nitric  acid,  and  precipitate  with 
ammonium  hydroxide.  Treat  the  precipitate  with  hot 
concentrated  ammonium  carbonate,  filter,  and  allow  the 
nitrate  to  cool.  The  double  carbonate  of  uranium  and 
ammonium  will  separate.  A  further  precipitate,  of  crude 
ammonium  uranate,  maybe  obtained  by  boiling  the  mother- 
liquor.  Uranium  salts  may  be  extracted  from  carnotite 
by  the  method  described  under  Vanadium,  Experiment  i, 
page  114,  the  sodium  hydroxide  precipitate  being  treated 
with  hot  concentrated  ammonium  carbonate,  as  directed 
above. 

Experiment   2.     Precipitation  of  sodium,   potassium,   or 

ammonium  uranate,  (R2U2Oy,  typical).  To  a  solution  of 
a  uranyl  salt  add  sodium,  potassium,  or  ammonium  hy- 
droxide. Note  the  yellow  color  of  the  precipitate  and  the 
insolubility  in  excess  of  the  reagent.  Repeat  the  experi- 
ment with  hydrogen  dioxide  present  in  the  solution. 

Experiment  3.  Formation  of  the  soluble  double  car- 
bonates of  uranium  with  sodium  or  potassium,  and  uranium 

with  ammonium,  (UO2CO3- 2^003)  •  (a)  To  a  solution  of 
a  uranyl  salt  add  a  solution  of  sodium  or  potassium  car- 
bonate, noting  the  first  and  the  final  effects.  Try  the  re- 
sult of  boiling,  and  of  adding  sodium  or  potassium  hydrox- 
ide to  a  separate  portion  of  the  clear  solution. 


EXPERIMENTAL   WORK  ON  URANIUM.  143 

(6)  Try  similarly  the  action  of  ammonium  carbonate 
upon  a  uranyl  salt  in  solution.  Note  the  ready  solvent 
action  of  an  excess  of  the  carbonate,  and  the  precipitation 
of  ammonium  uranate,  ((NH4)2U2O7),  on  boiling. 

(c)  To  a  solution  of  a  uranyl  salt  add  hydrogen  di- 
oxide and  potassium  or  sodium  carbonate.  Note  the 
cherry-red  color  (Aloy). 

Experiment  4.  Precipitation  of  uranyl  ferrocyanide, 
((UO2)3K2(FeC6N6)2  or  (UO2)2FeC6N6).  (a)  To  a  very 
dilute  solution  of  a  uranyl  salt  add  a  little  potassium  ferro- 
cyanide in  solution.  Note  the  red  precipitate.  This  is  a 
delicate  test  for  uranyl  salts.  The  precipitate,  which  is 
similar  in  color  to  that  formed  with  cupric  salts,  may  be 
distinguished  from  copper  ferrocyanide  by  its  decomposi- 
tion on  treatment  with  potassium  hydroxide  with  the 
formation  of  yellow  insoluble  potassium  uranate. 

(6)    Try  similarly  the  action  of  potassium  ferricyanide. 

Experiment  5.  Precipitation  of  uranyl  phosphate, 
(UO2HPO4).  To  a  solution  of  a  uranyl  salt  add  a  solution 
of  hydrogen  disodium  phosphate.  Try  the  action  of  the 
common  acids  upon  the  precipitate. 

Experiment  6.  Precipitation  of  uranyl  sulphide, 
(UO2S) .  (a)  To  a  solution  of  a  uranyl  salt  add  ammonium 
sulphide.  Note  the  dark-brown  color  of  the  precipitate, 
and  the  insolubility  in  excess  of  the  reagent. 

(b)  Try  the  action  of  hydrogen  sulphide  upon  a  uranyl  salt. 

Experiment  7.  Reduction  of  uranyl  salts .  (a)  To  a  solu- 
tion of  a  uranyl  salt  add  zinc  and  sulphuric  acid.  Note 
the  change  of  color  from  yellow  to  green. 

(b)  Bring  about  the  reduction  with  magnesium  and 
acid.  Test  the  uranous  salt  in  solution  with  potassium 
ferrocyanide  and  with  ammonium  sulphide. 

Experiment  8.  Bead  tests.  Fuse  a  little  of  a  uranium 
salt  in  a  borax  or  sodium  metaphosphate  bead.  Note  the 
yellow  color  in  the  oxidizing  flame  and  green  color  in  the 
reducing  flame. 


CHAPTER   IX. 

SELENIUM,  Se,  79.2. 

Discovery.  For  some  time  previous  to  the  discovery 
of  selenium  a  red  deposit  had  been  noticed  in  the  lead 
chambers  used  in  the  manufacture  of  sulphuric  acid  at 
Gripsholm  in  Sweden.  .  The  deposit  was  present  when  the 
sulphur  employed  had  been  prepared  from  pyrites  from 
Fahlun,  Sweden,  but  was  seldom  observed  when  the  sulphur 
had  been  obtained  from  other  sources.  At  first  the  un- 
known substance  was  supposed  to  be  sulphur.  When  it 
was  burned,  an  odor  as  of  decayed  cabbage  was  given  off, 
and  this  was  supposed  to  be  caused  by  the  presence  of 
tellurium  sulphide,  although  no  tellurium  could  be  ex- 
tracted from  the  material.  In  1817  Berzelius,  having 
become  a  shareholder  in  the  acid  works,  examined  the 
red  deposit,  and  in  a  short  time  he  announced  the  dis- 
covery of  a  new  element.  Because  of  its  frequent  associa- 
tion with  tellurium,  and  its  many  points  of  similarity  to 
that  element,  he  named  it  Selenium,  from  ae\rjvrf,  the 
moon  (Annal.  der  Phys.  u.  Chem.  (1818)  xxix,  229). 

Occurrence.  Selenium  is  found  usually  in  combination 
with  the  metals,  as  in  the  following  minerals : 

Clausthalite,  PbSe,  contains 27-28%  Se 

Tiemannite,  HgSe,  "       25-29%  " 

Guanajuatite,  Bi2Se3,  "        24-34%  " 

Naumannite,  (Ag2,Pb)Se,  "       27-30%  " 

Berzelianite,  Cu2Se,  "       39-40%  " 

Lehrbachite,  PbSe-HgSe,  "       24-28%" 

Eucairite,  Cu2Se  -Ag2Se,  "       31-32%  " 

Zorgite,  vid.  Clausthalite,  "       29-34%  " 

144 


SELENIUM.  145 

Crookesite,  (Cu,Tl,Ag)2Se,  contains 3o~33%Se 

Onofrite,  Hg(S,Se),  "       4-  6%  " 

Weibullite,  2 PbS -61483863,  "        0-14%" 

Chalcomenite,  CuSeO3-2H20,      "        48-49%  Se02 

Tellurium  (native),  Te,  "      6-  7%  Se 

Selen-sulphur,  ^Se-^S,  "       35~66%  " 

Selen-tellurium,  3X6  •  2Se,  "       29-3070" 

It  is  found  also  in  some  volcanic  lavas,  and  in  anode 
muds  in  electrolytic  copper  refineries. 

Extraction.  Selenium  salts  may  be  extracted  from  flue- 
dust  by  the  following  methods: 

(1)  The    soluble    material    is    dissolved    by    treatment 
with  water,  and  the  selenium  is  extracted  from  the  residue 
by  aqua  regia  (Berzelius,  vid.  Experiment   i). 

(2)  The  seleniferous  material  is  digested  with  a  solu- 
tion of  potassium  cyanide  at  a  temperature  of  8o°-ioo°  C. 
until  the  red  color  has  changed  to  gray,  (KSeCX).     The 
selenium  goes  into  solution  and  may  be  precipitated  by 
hydrochloric    acid    (Pettersson,    Ber.    Dtsch.    chem.    Ges. 
vii,    1719). 

(3)  The  flue-dust  or  mineral  is  fused  with  sodium  car- 
bonate, and  the  selenium  is  extracted  with  water  as  sodium 
selenide  and  selenite,   (Na2Se;  Na2SeO3). 

The  Element.  A.  Preparation.  Selenium  in  the  ele- 
mentary condition  may  be  prepared  by  the  action  (i)  of 
sulphur  dioxide,  zinc,  or  iron,  upon  selenious  acid  (Ber- 
zelius) ;  (2)  of  hydrochloric  acid  upon  sodium  seleno-sul- 
phite  (Pettersson) ;  (3)  of  potassium  iodide,  sodium  thio- 
sulphate,  etc.,  upon  selenious  acid. 

B.  Properties.  Like  sulphur,  selenium  is  known  in 
several  allotropic  modifications,*  and  may  be  either  soluble 

*  For  discussions  of  these  modifications,  see  Saunders,  Jour.  Phys.  Chem. 
(1900)  iv,  423;  Marc,  Physikalisch-chemischen  Eigenschaften  des  metallischen 
Selens,  pub.  by  Leopold  Voss,  Hamburg,  1907;  de  Coninck,  Bull.  Acad.  roy. 
Belgique  (1907),  365,  or  Chem.  Zentr.  (1907)  n,  575;  Pochettino,  Atti  Accad. 
Lincei,  Roma  [5]  xx  [i],  428. 


146  THE  RARER  ELEMENTS. 

or  insoluble  in  carbon  disulphide.  In  soluble  form  selen- 
ium is  a  red  powder  which  softens  at  5o°-6o°  C.,  is  partly 
fluid  at  100°  C.  and  is  completely  fused  at  250°  C  .  After 
it  has  been  melted  it  remains  in  a  plastic  condition  for  a 
long  time  and  has  a  metallic  luster.  Its  specific  gravity 
is  4.2  to  4.3.  From  a  warm  solution  in  carbon  disulphide 
the  element  separates  in  red,  monoclinic,  crystalline  plates, 
and  from  a  cold  solution  in  orange-red  monoclinic  crys- 
tals of  different  type.  The  specific  gravity  of  these  crys- 
talline varieties  is  4.4  to  4.5.  Selenium  insoluble  in  carbon 
disulphide  may  be  obtained  by  allowing  the  element  to 
cool  very  slowly  after  it  has  been  heated  to  a  higher  tem- 
perature than  i3o°C.,  or  by  allowing  the  oxygen  of  the 
air  to  act  upon  selenides  in  aqueous  solution.  Under 
these  conditions  the  element  assumes  the  so-called  metallic 
form,  crystallizes  in  steel-gray  hexagonal  crystals,  and 
becomes  isomorphous  with  tellurium.  Selenium  in  this 
form  is  a  poor  conductor  of  electricity,  but  when  heated  to 
about  200°  C.  it  becomes  a  good  conductor.  Metallic 
selenium  melts  at  217°  C.  without  previous  softening.  Its 
specific  gravity  is  4.8. 

Selenium  boils  at  700°  C.,  yielding  a  dark-yellow  vapor 
which,  when  condensed  and  cooled,  assumes  a  form  similar 
to  flowers  of  sulphur;  this  is  called  flowers  of  selenium. 
The  element  is  soluble  in  sulphuric  acid,  giving  a  green 
solution,  and  is  oxidized  by  nitric  acid  to  selenious  acid, 
(H2SeO3).  It  combines  with  metals  to  form  selenides. 
When  heated  in  air  or  oxygen  it  burns  with  a  blue  flame 
and  goes  over  to  the  dioxide,  (SeO2) .  It  is  a  poor  conductor 
of  heat  and  electricity. 

Compounds.*  A.  Typical  forms.  The  following  com- 
pounds of  selenium  may  be  considered  typical : 

*  Rimini,  Gaz.  chim.  ital.  xxxvn  [i],  261;  Pellini,  Atti  AccacJ.  Lincei,  Roma 
Is]  xv  [i],  629,  711;  [n],  46;  xvra  [n],  211;  or  Review  in  Jour.  Amer.  Chem.  Soc. 
XXDC,  395;  Vanino,  J.  prakt.  Chem.  xci,  116;  Gutbier,  Ztschr.  anorg.  Chem. 
rxxxK,  307. 


SELENIUM. 

Oxides  ............  SeO2 

Fluorides  ..........  SeF4        SeF6  ?  * 

Chlorides  .........  Se2Cl2         SeCl4 

SeCl3Br 
Oxychloride  .......  SeOCl2 

Bromides  .........  Se2Br2        SeBr4 

SeClBr3 
Iodides  ...........  Se2I2          SeI4 

Seleno-sulphite  ____  SeSO3 


Alums  ............  fgU^SeO,),  +  24H2O 

Thioselenic  acid.  .  .  H2SSeO3 

Thioseleniate  ......  K2SSeO3 

Cyanides  .........  (CN)2Se 

(CN)2Se3 

H(CN)Se 

K(CN)Se 

R(CN)Se2 
Nitride  ...........  N2Se 

Phosphides  .......  P4Se3 

P2Se5 
Selenides  ..........  H2Se 

CSe2 

NiSe 

Ag2Se 

Na2Se2,  Na2Se3,f  Na2SeO34  R2SeO4 

K2Se,  etc. 
Acids  (selenious  and  selenic)     H2SeO3,  H2SeO4 

Salts  (selenites  and  seleniates)  R2SeO3,  f  R2SeO4 

B.  Characteristics.  The  compounds  of  selenium,  as  will 
appear  later,  closely  resemble  those  of  tellurium,  both 
in  structure  and  in  behavior  toward  reagents.  They 

*  Ramsay,  Compt.  rend.  CXLIV,  1196;  Lebeau,  Compt.  rend.  CXLV,  190. 

f  Mathewson,  Jour.  Amer.  Chem.  Soc.  xxix,  867. 

J  For  selenites  of  the  rare  earths  see  Espil,  Compt.  rend,  cm,  378. 


I48  THE  RARER  ELEMENTS. 

are,  however,  rather  more  sensitive  to  the  action  of 
reducing  agents,  and  readily  precipitate  the  red  amor- 
phous variety  of  the  element,  which  tends  to  become 
black  when  heated.  Hydrogen  selenide  is  a  gas  which 
acts  like  hydrogen  sulphide  and  hydrogen  telluride, 

and  precipitates  the  selenides  (R2Se).  By  the  treatment 
of  elementary  selenium  with  nitric  acid  or  aqua  regia 
and  evaporation  to  dryness,  selenious  oxide,  (SeO2),  is 
formed,  which  dissolves  in  water,  forming  selenious  acid, 
(H2SeO3).  By  the  action  of  powerful  oxidizing  agents, 
such  as  chlorine,  bromine,  or  potassium  permanganate, 
selenious  acid  may  be  oxidized  to  selenic  acid,  (H2SeO4), 
which  is  not  reduced  by  sulphur  dioxide.  These  acids 

form  salts  of  the  types  R2SeO3  and  R2Se04.  By  the  action 
of  reducing  agents,  such  as  sulphur  dioxide  or  ferrous 
sulphate,  red  amorphous  selenium  may  be  readily  pre- 
cipitated from  selenious  acid.  Two  chlorides,  (Se2Cl2; 
SeCl4),  and  the  corresponding  bromides  and  iodides  are 
known.  When  selenium  is  heated,  a  characteristic,  pene- 
trating odor  is  given  off  which  has  been  variously  described 
as  like  that  of  garlic,  decayed  cabbage,  and  putrid  horse- 
radish. This  odor  is  caused  by  the  formation  of  small 
amounts  of  the  hydride. 

Estimation.  A.  Gravimetric.  Selenium  is  generally 
weighed  as  the  element,  obtained  by  treating  solutions 
of  its  compounds  (i)  with  sulphurous  acid  in  hydrochloric 
acid  solution;  (2)  with  potassium  iodide  in  acid  solution 
(Peirce,  Amer.  Jour.  Sci.  [4]  i,  416);  (3)  with  hypophos- 
phorus  acid  in  alkaline  solution  (Gutbier  and  Rohn,  Zeitsch. 
anorg.  Chem.  xxxiv,  448).  Other  reducing  agents  may  be 
used  (vid.  Gutbier,  Ztschr.  anal.  Chem.  LIV,  193). 

B.  Volumetric.  Selenium  may  be  determined  volu- 
metrically  (i)  by  oxidizing  selenious  acid  to  selenic  by 
means  of  standard  potassium  permanganate  in  sulphuric 
acid  solution,  using  an  excess  of  permanganate,  and  titrat- 


SELENIUM. 


149 


ing  back  with  oxalic  acid  (Gooch  and  demons,  Amer. 
Jour.  Sci.  [3]  L,  51)  ;  (2)  by  reducing  selenic  or  selenious  acid 
by  means  of  potassium  iodide  in  hydrochloric  acid  solution, 


and  determining  by  appropriate  means  the  iodine  set  free 
(Muthmann  and  Schaefer,  Ber.  Dtsch.  chem.  Ges.  xxvi, 
1008;  Gooch  and  Reynolds,  Amer.  Jour.  Sci.  [3]  L,  254); 
(3)  by  reducing  selenic  acid  to  selenious  by  boiling  with 
hydrochloric  acid,  (SeO3  +  2HCl=SeO2  +  H2O  +  Cl2),  then 
passing  the  free  chlorine  into  potassium  iodide,  and  deter- 
mining the  iodine  set  free  (Gooch  and  Evans,  Amer.  Jour. 
Sci.  [3]  L,  400)  ;  (4)  by  employing  potassium  bromide  and 
sulphuric  acid  instead  of  hydrochloric  acid  in  (3)  (Gooch 
and  Scoville,  Amer.  Jour.  Sci.  [3]  L,  402)  ;  (5)  by  boiling 
a  solution  of  selenious  acid  with  sulphuric  acid,  a  known 
amount  of  potassium  iodide,  and  an  excess  of  arsenic  acid; 
the  reduction  of  the  selenious  acid  will  decrease  the  reduction 
of  arsenic  acid;  the  quantity  of  arsenious  acid  present  at 
the  close  of  the  action  may  be  measured,  after  neutral- 
ization with  potassium  bicarbonate,  by  standard  iodine 
(Gooch  and  Peirce,  Amer.  Jour.  Sci.  [4]  i,  31);  (6)  by  the 
reduction  of  selenious  acid  to  elementary  selenium  by 
means  of  standard  sodium  thiosulphate  solution  in  excess 
in  the  presence  of  hydrochloric  acid,  —  the  excess  of  thio- 
sulphate being  determined  by  standard  iodine  solution 
(Norris  and  Fay,  Amer.  Chem.  Jour,  xvm,  703;  Norton, 
Amer.  Jour.  Sci.  [4]  vn,  287)  ;  (7)  by  boiling  elementary 
selenium  with  ammonia  and  standard  silver  nitrate  solution, 
acidifying  with  nitric  acid,  and  determining  the  excess 
of  silver  nitrate  by  ammonium  sulpho-cyanide,  with  ferric 
alum  as  indicator;  the  quantity  of  selenium  present  is 
calculable  from  the  quantity  of  silver  nitrate  used,  as  is 
shown  in  the  following  equation:  4AgNO3  +  3Se  +  3H2O 
=  2Ag2Se  +  H2SeO3  +  4HNO3  (Friedrich,  Zeitsch.  angew. 
Chem.  xv,  852). 

Separation.     Selenium  is   separated,  together  with  tel- 


ISO  THE  RARER  ELEMENTS. 

lurium,  from  other  elements  by  methods  given  under 
Tellurium,  where  the  separation  of  these  two  elements 
from  each  other  is  also  discussed. 


EXPERIMENTAL  WORK   ON    SELENIUM. 

Experiment  i.  Extraction  of  selenium  from  (i)  flue- 
dust  and  (2)  seleniferous  residues  from  electrolytic  refining  of 
copper,  (i)  Treat  about  25  grm.  of  the  washed  flue-dust 
with  aqua  regia  as  long  as  any  evidence  of  action  is 
observed,  and  evaporate  to  dryness.  Extract  the  residue 
with  about  25  cm.3  of  strong  common  hydrochloric  acid, 
and  filter.  To  the  filtrate  add  about  a  gram  of  dry  ferrous 
sulphate,  and  warm  gently  if  necessary.  Filter  off  the  red 
amorphous  selenium. 

(2)  Treat  about  25  grm.  of  the  residues  with  strong 
commercial  hydrochloric  acid,  warm  as  long  as  anything 
appears  to  dissolve,  and  filter.  Precipitate  the  selenium 
as  in  (i).  Save  the  filtrate  to  be  examined  later  for  tel- 
lurium. 

Experiment  2.  Preparation  of  selenium  dioxide,  (SeO2). 
To  a  small  amount  of  elementary  selenium  add  nitric  acid 
until  the  oxidation  is  shown  to  be  complete  by  the  cessation 
of  the  evolution  of  red  fumes  (oxides  of  nitrogen) .  Evapor- 
ate to  dryness  and  warm  gently.  The  white  residue  is 
selenium  dioxide.  Dissolve  this  in  a  little  water  to  form 
selenious  acid,  (H2SeO3). 

Experiment  3.  Precipitation  of  selenites.  (a)  To  a  little 
selenious  acid  add  a  few  drops  of  a  barium  salt  in  solution. 
Test  the  action  of  hydrochloric  acid  upon  the  precipitate. 

(b)  Try  the  action  of  cupric  sulphate  upon  a  little  sele- 
nious acid. 

(c)  Try  similarly  the  action  of  a  solution  of  mercurous 
nitrate. 

Experiment  4.  Formation  of  selenic  acid  (H^SeO^. 
(a)  To  a  few  cm.3  of  selenious  acid  add  first  a  small  amount 


EXPERIMENTAL  WORK  ON  SELENIUM.  I5r 

of  sulphuric  acid  and  then  a  solution  of  potassium  per- 
manganate until  the  purple  color  is  permanent.  Bleach 
by  the  careful  addition  of  oxalic  acid. 

(6)  Pass  chlorine  gas  into  water  in  which  some  ele- 
mentary selenium  is  suspended. 

Experiment  5.  Reactions  with  selenic  acid,  (a)  To  a 
solution  of  selenic  acid  formed  as  in  4  (6)  add  a  little 
barium  salt  in  solution.  Note  the  precipitation  of  barium 
selenate  (BaSeO4). 

(6)  Try  the  action  of  a  solution  of  cupric  sulphate 
upon  a  solution  of  selenic  acid.  Compare  with  3  (6). 

(c)  To  a  solution  of  selenic  acid,  free  from  chlorides,  add 
a  little  mercurous  nitrate  in  solution.  Note  the  precipitate 
of  mercurous  selenate  (Hg2SeO4). 

Experiment  6.  Reduction  of  selenic  acid  to  selenious. 
Add  to  a  given  volume  of  selenic  acid  half  as  much  strong 
hydrochloric  acid  and  boil  to  about  two  thirds  of  the  total 
volume.  Note  the  evolution  of  chlorine.  Test  by  starch 
iodide  paper. 

Experiment  7.  Precipitation  of  elementary  selenium. 
Try  the  action  of  the  following  reducing  agents  upon  dilute 
selenious  acid:  sulphur  dioxide,  hydrogen  sulphide,  acid 
sodium  sulphite,  potassium  iodide,  stannous  chloride, 
ferrous  sulphate. 

Experiment  8.  Solvent  action  of  carbon  disulphide  upon 
selenium.  To  a  little  dry,  washed,  amorphous  selenium 
add  carbon  disulphide.  Filter,  and  allow  the  filtrate  to 
evaporate. 

Experiment  9.  Solvent  action  of  potassium  cyanide  upon 
selenium.  To  a  small  amount  of  the  red  amorphous  sele- 
nium add  a  few  cm.3  of  a  dilute  solution  of  potassium 
cyanide  (poison !) ,  warm  gently,  and  filter.  To  the  filtrate 
add  hydrochloric  acid. 

Experiment  10.  Behavior  of  selenium  when  subjected  to 
heat.  Heat  a  small  amount  of  elementary  selenium  on  a 
glass  rod.  Note  the  odor,  and  the  color  of  the  flame. 


152  THE  RARER  ELEMENTS. 

Experiment  n.  Action  of  strong  sulphuric  acid  upon 
selenium.  To  a  small  amount  of  elementary  selenium  add 
a  few  cm.3  of  strong  sulphuric  acid  and  warm.  Note  the 
green  color.  Allow  to  cool  and  add  water.  Note  the 
precipitation  of  the  selenium  (SeS03  +  H2O^H2SO4 


TELLURIUM,  Te,   127.5.* 

Discovery.  Native  tellurium,  which  is  quite  widely 
distributed  in  small  quantities,  was  a  puzzle  to  the  early 
mineralogists.  Because  of  its  non-metallic  properties  and 
its  metallic  luster  it  was  known  as  aurum  paradoxum  and 
metallum  problematicum.  In  1782  Miiller  von  Reichen- 
stein,  after  some  careful  work  on  this  interesting  substance, 
suggested  that  a  peculiar  metal  might  be  present.  Acting 
on  the  suggestion,  Klaproth  undertook  an  investigation, 
and  in  1798  he  demonstrated  that  the  "metal"  was  not 
identical  with  any  known  element.  He  proposed  the 
name  Tellurium,  from  tellus,  earth  (Crell  Annal.  (1798)  i, 
91). 

Occurrence.  Tellurium  occurs  in  combination  and  also, 
sparingly,  native. 

Petzite,]  (Ag,Au)2Te,  contains..   32-35%  Te 

Goldschmidtite,  Au2AgTe6,  "       .  .   59-60%    " 

Hessite,  Ag2Te,  "       ..37-44%    " 


*  See  Lenher,  Jour.  Amer.  Chem.  Soc.  xxx,  741,  for  a  review  of  the  work  on 
the  homogeneity  of  tellurium.  Marckwald  (Ber.  Dtsch.  chem.  Ges.  XL,  4730) 
claims  that  previous  atomic  weights  have  been  defective,  and  gives  126.85  as 
the  result  of  his  work.  Later  (XLIII,  710)  by  means  of  volumetric  methods  he 
arrives  at  127.6  as  the  result.  Browning  and  Flint  and  later  Flint  (Amer.  Jour. 
Sci.  [4]  xxvin,  347;  xxx,  209)  obtained  a  value  approaching  126.5.  Harcourt 
and  Baker  (Jour.  Chem.  Soc.  (London)  xcix,  1311)  reaffirm  127.5  and  Dennis  and 
Anderson  (Jour.  Amer.  Chem.  Soc.  xxxvi,  882)  reach  the  same  conclusion.  For  a 
discussion  of  the  whole  subject  see  Pellini,  Ueber  das  Atomgewicht  des  Tellurs, 
pub.  by  Ferd.  Enke,  Stuttgart,  1915. 

t  Pellini,  Gazz.  chim.  ital.  XLV,  I,  469. 


TELLURIUM.  153 

Empressite,  AgTe,  contains..   54-55%  Te 

Altaite,  PbTe,  "  ..  37-38%  " 

Coloradoite,  HgTe,  "  . .   38-39%  " 

Melonite,  Ni2Te3,  "  . .   73-76%  " 

Kalgoorlite,  HgAu2Ag6Te6,  "  ..37-56%  " 

Sylvanite,  (Au,Ag)Te2,  "  . .   58-62%  " 

Calaverite,  (Au,Ag)Te2-AuTe2,  "  ..   56-58%  " 

Krennerite,  (Au,Ag)Te2-AuTe2,  "  ..38-59%  " 

Muthmannite,  (Au,Ag)Te  "  . .  46-47%  " 

Nagyagite,  Au2Pbi4Sb3Te7Si7,  "  ..   15-31%  " 

Goldfieldite,  5Cu2S(Sb,Bi,As)2(S,Te)3 "  . .         17%  " 

Tapalpite,  3Ag2(S,Te)-Bi2(S,Te)3?,     "  ..20-24%  " 

Von  Diestite,  #Ag2Te  •  ;yBi2Te3  "  .  .   34-35%  " 

Tetradymite,  Bi2Te3S3)*  "  . .   33-49% 

Griinlingite,  Bi4TeS3,  "  .  .    12-13^  " 

Rickardite,  Cu2Te  •  2CuTe,  "  ..    59-60^  <( 

Joseite,  formula  doubtful,  "  ..    i5~i6r('  " 

Wehrlite,     "            "  "  ..   29-35%  " 

Stutzite,  Ag4Te?,  "  ..    22-23^  " 

Tellurite,  TeO2,  "  ..    79-80%  " 

Montanite,  Bi2(OH)4TeO6?,  "  .  .    24-28%  TeO3 

Emmonsite,  formula  doubtful,  "  .  .    59-60^  Te 

Durdenite,  Fe2(TeO3)3-4H2O,  "  ..    47-64^  Te02 

Tellurium  (native),  Te,  "  ..    93-97%  Te 

Selen-tellurium,  3Te2Se,  "  ..    70-71%  " 

Tellurium  is  found  also  in  residues  from  the  electrolytic 
*Tefining  of  copper,  and  in  flue-dust  from  smelters  working 
telluride  gold  ores. 

Extraction.  Tellurium  may  be  extracted  by  the  follow- 
ing methods : 

(i)  From  tellurium  bismuth  (tetradymite) .  The  mineral 
is  mixed  with  its  own  weight  of  sodium  carbonate,  and 
oil  is  added  until  the  mass  has  the  consistency  of  thick 

*  Amadori,  Atti  accad.  Lincei  xxrv,  II,  200. 


I54  THE  RARER  ELEMENTS. 

paste.  This  is  heated  strongly  in  a  well-closed  crucible 
and  then  extracted  with  water.  The  extract,  containing 
sodium  sulphide  and  sodium  telluride,  (Na2Te),  is  separated 
by  filtration  from  the  insoluble  matter  and  left  exposed 
to  the  air.  The  tellurium  separates  as  a  gray  powder.  It 
may  be  purified  by  distillation  (Berzelius). 

(2)  From  sylvanite  or  nagyagite.     The  mineral  is  treated 
with    hydrochloric    acid,    which    dissolves    the    antimony, 
arsenic,  etc.     The  residue  is  dissolved  in  aqua  regia,  the 
excess  of  acid  is  removed  by  evaporation,  and  the  gold  is 
precipitated  by  ferrous   sulphate.     After  the  removal  of 
the  gold  by  filtration  the  tellurium  is  precipitated  by  sul- 
phur dioxide   (Von  Schrotter). 

(3)  From  flue-dust  containing  tellurium.     The  material 
is  treated  with  strong  commercial  hydrochloric  acid  (vid. 
Experiment  i). 

The  Element.  A.  Preparation.  Elementary  tellurium 
may  be  obtained  (i)  by  the  action  of  reducing  agents,  as 
sulphurous  acid,  stannous  chloride,  or  hydrazine  upon  the 
salts  of  tellurium;  and  (2)  by  the  action  of  air  upon  soluble- 
tellurides. 

B.  Properties.  Tellurium  is  generally  considered  a  non- 
metal,  though  Berzelius  classed  it  with  the  metals.  It  is 
known  in  two  conditions:  (i)  the  crystalline,  in  which  the 
element  has  a  luster  like  silver,  and  (2)  the  amorphous.  It 
is  unchanged  in  the  air  at  ordinary  temperatures,  but  when 
heated  in  air  or  oxygen  it  burns  with  a  green  flame,  forming; 
the  dioxide  (TeO2).  It  is  not  attacked  by  hydrochloric 
acid,  but  is  acted  upon  slowly  by  concentrated  sulphuric 
acid,  with  evolution  of  sulphur  dioxide.  It  is  oxidized  by 
nitric  acid  and  aqua  regia  to  tellurous  acid,  (H2TeO3),  and 
is  dissolved  in  hot  caustic  potash,  forming  the  telluride 
and  tellurite  (K2Te;  K2TeO3).  It  combines  with  metals 
to  form  tellurides  and  some  alloys.  Like  selenium  and 
sulphur,  it  is  a  poor  conductor  of  heat  and  electricity.  Its- 
specific  gravity  is  from  6.1  to  6.3. 


TELLURIUM.  155 

Compounds.  A.  Typical  forms.  -The  following  are  typ- 
ical compounds  of  tellurium: 

Oxides TeO  Te02  TeO3 

Chlorides  * TeCl2  TeCl4 

Oxychloride TeOCl2 

Bromides .  .TeBr2  TeBr4 

Oxybromide TeOBr2 

Iodides TeI2  TeI4 

Fluoride TeF4 

Double  fluoride TeF4  •  KF 

Nitrate  (basic)' Te2O3(OH)NO3 

Sulphite TeSO3 

Sulphate 2Te02-SO3 

Sulphides  (or  sulpho  salts) .  TeS2  •  3  K2S 

TeS2-Bi2S3,  etc. 
Tellurides H2Te,  tCTe2J 

As2Te3 

K2Te,  etc. 

Acids  (tellurous  and  telluric)  H2TeO3§   H2Te04  ]| 

Salts  (tellurites  and  tellurates)  R2TeO3      R2TeO4 

B.  Characteristics.  The  compounds  of  tellurium  closely 
resemble  in  general  structure  those  of  sulphur  and  sele- 
nium. Hydrogen  telluride,  (H2Te),  like  hydrogen  sulphide, 
is  a  gaseous  substance,  and  it  precipitates  metallic  tel- 

lurides,  (R2Te),  similar  to  the  sulphides.  Two  oxides, 
tellurous  (TeO2),  and  telluric,  (TeO3),  are  well  known,  ^ 
but,  unlike  the  corresponding  oxides  of  sulphur,  they 

*  For  an  extended  discussion  of  the  halogen  salts  see  Gutbier,  Jour,  prakt. 
Chem.  [2]  LXXXIII,  145;  Ztschr.  anorg.  Chem.  LXXXVT,  169. 

f  Dennis  and  Anderson,  Jour.  Amer.  Chem.  Soc.  xxxvi,  882. 

t  Stock,  Ber.  Dtsch.  chem.  Ges.  XLIV,  1832. 

§  Lenher,  Jour.  Amer.  Chem.  Soc.  xxxv,  718. 

||  Gutbier  favors  the  formula  H6TeO6.  See  also  Staudenmeier,  Zeitsch.  anorg; 
Chem.  x,  189;  Gutbier,  Zeitsch.  anorg.  Chem.  XL,  260;  J.  prakt.  Chem.  LXXXV. 
321;  LXXXVI,  150;  Faber,  Zeitsch.  anal.  Chem.  XLVI,  277. 

T  A  monoxide,  (TeO),  also  has  been  described. 


156  THE  RARER  ELEMENTS. 

are  very  sparingly  soluble  in  water.  The  acids,  (H2TeOs; 
H2TeO4),  may  be  formed  by  acidifying  solutions  of  the 
alkali  salts  (e.g.,  Na2Te03  or  Na2TeO2)  which  have  been 
formed  by  the  action  of  the  alkali  hydroxides  upon 
the  oxides  (TeO2;  TeO3).  Many  tellurites  and  tellurates, 
(I^TeOg;  R2TeO4),  may  be  formed  by  treating  the  alkali 
tellurites  or  tellurates  with  soluble  salts  of  the  various 
bases.  Two  chlorides  are  known,  (TeCl2;  TeCl4),  both  of 
which  are  decomposed  by  water.  The  corresponding 
bromides  and  iodides  are  also  known.  In  general,  com- 
pounds of  tellurium  are  easily  reduced  to  the  element. 
The  reduction,  however,  is  not  accomplished  quite  so 
readily  as  in  the  case  of  selenium  compounds. 

Estimation.*  A.  Gravimetric.  Tellurium  is  usually 
weighed  as  the  element,  obtained  by  treating  solutions 
of  tellurium  compounds  (i)  with  sulphur  dioxide;  (2) 
with  hydrazine  sulphate  in  ammoniacal  solution  (Jan- 
nasch,  Ber.  Dtsch.  chem.  Ges.  xxxi,  2377);  (3)  with  hydra- 
zine hydrate  or  its  salts  in  acid  or  alkaline  solution  (Gut- 
bier,  Ber.  Dtsch.  chem.  Ges.  xxxiv,  2724);  (4)  with  sul- 
phur dioxide  and  potassium  iodide  (Frericks,  J.  pr.  Chem. 
[2]  LXVI,  261);  (5)  with  hypophosphorus  acid  (Gutbier, 
Zeitsch.  anorg.  Chem.  xxxn,  295) ;  (6)  with  grape-sugar 
in  alkaline  solution  (Stolba,  vid.  Kastner,  Zeitsch.  anal. 
Chem.  xiv,  142);  (7)  with  acid  sodium  sulphite  or  mag- 
nesium (vid.  Experiment  i) ;  (8)  with  sulphur  dioxide  and 
hydrazine  hydrochloride  (Lenher,  Jour.  Amer.  Chem.  Soc. 
xxx,  387). 

It  may  be  weighed  also  as  the  sulphate,  (2TeO2-SO3), 
obtained  by  treating  elementary  tellurium  with  a  mixture 


*See  Gutbier,  Studien  iiber  das  Tellur,  pub.  by  Hirschfeld,  Leipzig,  1902; 
Mac  Ivor,  Chem.  News,  LXXXVII,  17,  162. 


TELLURIUM.  157 

of    nitric  and  sulphuric  acids  and  evaporating  (Metzner, 
Ann.  Chim.   Phys.  [7]  xv,   203). 

B.  Volumetric.  Tellurium  may  be  estimated  volumet- 
rically  (i)  by  the  reduction  of  telluric  acid  to  tellurous  by 
means  of  potassium  bromide  in  sulphuric  acid  solution, 
(H2TeO4  +  2HBr  =  H2TeO3  +  H2O  +  Br2),  the  bromine  being 
passed  into  potassium  iodide,  and  the  iodine  estimated 
by  standard  thiosulphate  (Gooch  and  Howland,  Amer. 
Jour.  Sci.  [3]  XLVIII,  375);  (2)  by  the  reducing  action  of 
strong  hydrochloric  acid  upon  soluble  tellurates,  chlorine 
being  set  free  and  passed  into  potassium  iodide  with  libera- 
tion of  iodine,  as  above;  (3)  by  the  action  of  standard 
potassium  iodide  solution  upon  a  solution  of  tellurous 
acid  containing  twenty-five  per  cent,  by  volume  of  strong 
sulphuric  acid,  (H2TeO3  +  4H2SO4  +  4KI  =TeI4  +  4KHSO4  + 
3H2O),  tellurous  iodide  being  precipitated  as  a  black,  curdy 
mass,  which,  when  shaken,  separates  in  such  a  manner  that 
the  point  when  precipitation  ceases  can  easily  be  detected ; 
the  quantity  of  tellurium  present  is  calculable  from  the 
quantity  of  potassium  iodide  used  (Gooch  and  Morgan, 
Amer.  Jour.  Sci.  [4]  n,  271);  (4)  by  the  oxidation  of  tellu- 
rous acid  by  means  of  standard  potassium  permanganate 
in  acid  or  alkaline  solution  (Norris  and  Fay,  Amer.  Chem. 
Jour,  xx,  278;  Gooch  and  Peters,  Amer.  Jour.  Sci.  [4] 

VIII,    122). 

Separation.*  From  the  elements  not  easily  reduced 
from  their  compounds  to  elementary  form,  tellurium  may 
be  separated  in  general  by  the  action  of  sulphur  dioxide  in 
faintly  acid  solution ;  this  precipitates  elementary  tellurium. 
From  bismuth  tellurium  is  separated  by  the  action  of 
potassium  sulphide  upon  the  precipitate  thrown  down 
from  solutions  by  hydrogen  sulphide, — the  tellurium  dis- 

*  See  Gutbier,  Studien  uber  das  Tellur. 


158  THE  RARER  ELEMENTS. 

solving.  From  antimony  the  separation  may  be  accom- 
plished (i)  by  hydrazine  hydrate,  the  tellurium  being  pre- 
cipitated (Gutbier,  Zeitsch.  anorg.  Chem.  xxxn,  260); 
(2)  by  treatment  of  a  solution  of  sulpho-tellurite  and  sul- 
pho-antimonite  with  20%  hydrochloric  acid  in  the  pres- 
ence of  tartaric  acid,  the  tellurium  separating  out  (Muth- 
mann  and  Schroder,  Zeitsch.  anorg.  Chem.  xiv,  433).  From 
silver  tellurium  is  separated  by  hydrochloric  acid,  the 
silver  being  precipitated;  from  gold  by  the  action  of  heat 
on  the  two  metals,  tellurium  being  volatilized;  from  mer- 
cury by  the  action  of  phosphorus  acid  upon  a  cold  dilute 
hydrochloric  acid  solution  of  the  salts,  mercurous  chloride 
being  precipitated. 

From  selenium  tellurium  may  be  separated  (i)  by 
hydroxylamine  in  strong  hydrochloric  acid  solution,  the 
selenium  being  precipitated  (Jannasch  and  Muller,  Ber. 
Dtsch.  chem.  Ges.  xxxi,  2388);  (2)  by  sulphur  dioxide  in 
strong  hydrochloric  acid  solution,  selenium  being  pre- 
cipitated (Keller,  Jour.  Amer.  Chem.  Soc.  xix,  771,  and 
xxn,  241);  (3)  by  fusion  of  the  elements  with  potassium 
cyanide  in  the  presence  of  hydrogen,  tellurium  being  pre- 
cipitated when  air  is  passed  through  a  solution  of  the  melt ; 

(4)  by  the  action  of  ferrous  sulphate  (vid.   Experiment  i) ; 

(5)  by  the  greater  volatility  of  the  bromide  of  selenium 
(Gooch  and  Peirce,  Amer.  Jour.  Sci.  [4]  i,  181);  (6)  by  the 
action  of  acetic  acid  on  a  solution  of  an  alkali  tellurite  and 
selenite,  tellurous  acid  being  precipitated  (Browning  and 
Flint,  Amer.  Jour,  Sci.  [4]  xxvin,  112). 

EXPER.IMENTAL  WORK  ON  TELLURIUM. 

Experiment  i.  Extraction  of  tellurium  from  flue-dust,  or 
jrom  waste  products  from  the  electrolytic  refining  of  copper, 
(a)  Treat  about  10  grm.  of  the  material  with  strong  com- 
mercial hydrochloric  acid  until  nothing  further  dissolves, 


EXPERIMENTAL  WORK   ON    TELLURIUM.  159 

and  filter.  To  a  small  portion  of  the  filtrate  add  ferrous 
sulphate,  and  warm  gently.  The  presence  of  selenium  will 
be  indicated  by  a  reddish  precipitate.  If  selenium  has  thus 
been  shown  to  be  present,  take  about  5  cm.3  of  the  original 
filtrate,  precipitate  the  selenium  and  tellurium  by  acid 
sodium  sulphite  or  by  magnesium,  wash  this  precipitate, 
return  it  to  the  remainder  of  the  filtrate,  and  heat  to  boil- 
ing. The  selenium  present  will  be  precipitated  by  the 
tellurium.  Remove  the  selenium  by  filtration  and  set  it 
aside.  From  the  filtrate  precipitate  the  tellurium  by  acid 
sodium  sulphite  or  by  magnesium  (Crane,  Amer.  Chem. 
Jour,  xxm,  408). 

(6)  Treat  the  residues  with  ammonium  hydroxide  as 
long  as  anything  appears  to  dissolve.  Filter,  and  acidify 
the  filtrate  with  acetic  acid.  The  tellurous  acid  is  pre- 
cipitated and  the  selenious  acid  remains  in  solution.  The 
tellurous  acid  may  be  further  purified  by  dissolving  the 
precipitate  in  sodium  hydroxide  and  reprecipitating  with 
acetic  acid.  Dissolve  in  hydrochloric  acid  and  precipitate 
the  element  as  in  (a)  (Browning). 

Experiment  2.  Action  of  strong  sulphuric  acid  upon  tel- 
lurium. To  a  small  amount  of  elementary  tellurium  add  a 
few  cm.3  of  strong  sulphuric  acid  and  warm.  Note  the 
reddish-violet  color.  This  reaction  constitutes  a  good  test 
for  tellurium.  Allow  to  cool  and  add  water.  (See  Sele- 
nium, Experiment  u). 

Experiment  3.  Preparation  of  tellurium  dioxide,  (Te02). 
To  a  small  amount  of  elementary  tellurium  add  nitric  acid, 
evaporate  to  dryness,  and  heat  gently. 

Experiment  4.  Formation  of  an  alkali  tellurite,  (R2TeO3). 
Dissolve  a  little  tellurium  dioxide  in  a  solution  of  sodium 
or  potassium  hydroxide. 

Experiment  5.  Formation  of  telluric  acid,  (H2TeO4). 
(a)  To  a  solution  of  an  alkali  tellurite  add  sulphuric  acid 
until  the  precipitate  first  formed  dissolves.  Then  add  grad- 
ually a  solution  of  potassium  permanganate  until  no  further 


160  THE  RARER  ELEMENTS. 

bleaching  action  is  noticed.  (6)  To  an  alkaline  solution  of 
an  alkali  tellurite  add  hydrogen  dioxide  and  warm. 

Experiment  6.  Reduction  of  telluric  acid.  To  a  solution 
of  telluric  acid  prepared  in  the  previous  experiment 
add  a  little  potassium  bromide  and  sulphuric  acid,  and  boil. 
Note  the  evolution  of  bromine  and  the  reduction  to  tellu- 
rous  acid. 

Experiment  7.  Precipitation  of  tellurous  iodide,  (TeI4). 
To  a  solution  of  an  alkali  tellurite  add  sulphuric  acid  until 
the  precipitate  first  formed  dissolves.  Then  add  a  few 
drops  of  a  solution  of  potassium  iodide.  Note  the  black 
precipitate. 

Experiment  8.  Action  of  potassium  cyanide  upon  tellu- 
rium. Fuse  a  small  amount  of  elementary  tellurium 
with  potassium  cyanide  out  of  contact  with  the  air 
(2KCN  +  Te  =  K2Te  +  (CN)2) .  Extract  with  water  and  pass 
air  through  the  solution.  Note  the  precipitation  of  tellu- 
rium. 

Experiment  9.  Precipitation  of  elementary  tellurium. 
(a)  Try  the  action  of  the  following  reducing  agents  upon 
separate  portions  of  the  filtrate  obtained  in  Experiment  i 
(2),  Selenium,  or  of  any  acid  solution  containing  tellurium: 
stannous  chloride,  hydrogen  sulphide,*  sulphurous  acid, 
magnesium,  and  acid  sodium  sulphite. 

(6)  Try  the  action  of  an  alkali  stannite  upon  a  solution 
of  an  alkali  tellurite. 

Experiment  10.  Action  of  tellurium  compounds  before 
the  blowpipe.  Heat  on  charcoal  a  small  amount  of  a  tellu- 
rium compound.  Note  the  white  sublimate  and  the  green 
color  imparted  to  the  reducing  flame. 

Experiment  n.  Negative  test  of  tellurium.  Try  the 
action  of  ferrous  sulphate  upon  an  acidified  solution  of  a 
tellurite. 

*  Some  authors  give  TeSz  or  TeS+S  as  the  constitution  of  the  precipitate  by 
hydrogen  sulphide  (Snelling,  Jour.  Amer.  Chem.  Soc.  xxxiv,  802). 


CHAPTER  X. 

PLATINUM,  Pt,   195.2. 

Discovery.  In  the  year  1750  William  Watson  presented 
to  the  Royal  Society  a  communication  from  William 
Brownrigg  in  which  was  described  a  "semi-metal  called 
Platina  di  Pinto ' '  found  in  the  Spanish  West  Indies.  Wat- 
son stated  that,  so  far  as  he  knew,  no  previous  mention  had 
been  made  of  this  substance  except  by  Don  Antonio  de 
Ulloa  in  the  history  of  his  voyage  to  South  America,  pub- 
lished in  Madrid  in  1748  (Phil.  Trans.  Roy.  Soc.  (1750) 
XLVI,  584).  However,  an  earlier  discovery  is  suggested  by 
a  statement  of  Scaliger  in  1558,  who,  in  combating  the 
opinion  of  Cardanus,  that  all  metals  are  fusible,  declared 
that  an  infusible  metallic  substance  existed  in  the  mines  of 
Mexico  and  Darien.  As  platinum  is  found  in  those  coun- 
tries, it  is  probably  the  metal  referred  to.  The  name 
Platinum  is  derived  from  the  Spanish  platina,  the  diminu- 
tive of  plata,  silver. 

Occurrence.  Platinum  occurs  alloyed  with  the  various 
metals  of  its  group — palladium,  osmium,  iridium,  etc. — and 
associated  with  other  metals,  as  iron,  lead,  copper,  titanic 
iron,  etc.  It  is  found  chiefly  in  the  Ural  Mountains,*  asso- 
ciated with  chrome  iron  ore,  magnetite,  cinnabar,  diamonds, 
and  gold,  but  also  in  Brazil,  Mexico,  Borneo,  Calif ornia.f 

*  See  Duparc,  Arch.  Sc.  phys.  et  nat.  Geneve  [4]  xxxi,  211,  322,  439,  456,  516; 
Friwoznic,  Oesterr.  Ztschr.  f.  Berg-  u.  Huttenwesen,  LX,  143,  155. 

t  See  Mineral  Resources,  U.  S.  (1910),  page  773;    (1914),  333J    Keller,  J. 
Franklin  Inst.  CLXXIV,  525. 

161 


16*  THE  R4RER  ELEMENTS. 

Oregon,  Washington,  and  elsewhere.  The  Brazilian  sources 
have  recently  come  into  prominence,  and  Hussak  (Zeitsch. 
f.  Geo.  xiv,  284)  has  described  three  types  of  ore  from  that 
country.  The  first  is  similar  to  the  Uralian  platinum  in 
composition  and  associated  minerals.  The  second  contains 
no  gold  or  silver,  is  not  associated  with  magnetite  or 
chromite,  and  often  contains  as  much  as  21%  of.  palladium. 
It  occurs  with  rutile,  xenotime,  and  diamonds.  The  third 
type  is  free  from  iron,  poor  in  palladium,  and  occurs  with 
quartz  and  tourmaline.  Some  of  the  Brazilian  ores  contain 
from  73%  to  83%  of  platinum. 

Platinum  comprises  usually  from  fifty  to  eighty  per  cent, 
of  the  alloys  in  which  it  occurs.  It  is  found  combined  in 
the  mineral  sperrylite,  PtAs2,  which  contains  about  fifty- 
three  per  cent,  of  the  metal. 

Extraction.  Platinum  may  be  extracted  from  its  alloys 
by  the  following  methods : 

(1)  Fusion  process.    The  material  is  fused  with  sulphide 
of  lead.     The  iron  present   combines  with   the  sulphur. 
The  platinum  alloys  with  the  lead,  while  the  osmium  and 
iridium  do  not.    The  lead-platinum  alloy  is  separated  from 
the  mass  and  cupelled.    The  platinum  is  left  (Deville  and 
Debray). 

(2)  Wet  process.     The  pulverized  alloy  is  heated  in  a 
porcelain  dish  with  aqua  regia  as  long  as  action  continues. 
The  solution  obtained  is  nearly  neutralized  with  calcium 
hydroxide,  and  the  iron,  copper,  rhodium,  iridium,  and  part 
of  the  palladium  separate.     After  the  removal  of  these,  the 
filtrate  is  evaporated  to  dryness  and  the  residue  is  ignited 
and  treated  with  water  and  hydrochloric  acid.     The  plati- 
num, with  traces  of  the  platinum  metals,  remains. 

The  Element.  A.  Preparation.  As  extracted  from  its 
alloys,  platinum  is  in  the  elementary  condition  (vid.  Ex- 
traction) . 

B.  Properties.  In  its  usual  form,  elementary  platinum 
is  a  grayish-white  metal  which  is  very  malleable  and 
ductile,  but  fusible  only  in  the  oxyhydrogen  blowpipe  flame 


PLATINUM.  163 

or  by  means  of  the  electric  current.  Nernst*  has  deter- 
mined its  melting-point  as  1745°  C.,f  GuntzJ  has  found  it 
somewhat  volatile  at  fromiooo°C.toi3oo°C.,and  Moissan§ 
has  volatilized  it  in  the  electric  furnace.  At  no  temperature 
is  it  oxidized  by  water  or  oxygen.  Quennessen  1 1  finds  it  to 
be  slightly  soluble  in  sulphuric  acid  in  the  presence  of 
oxygen,  and  Marie  1j  states  that  it  is  oxidized  by  acid  and 
alkaline  permanganate,  by  persulphates,  chlorates,  bi- 
chromates, alkaline  ferricyanide,  and  concentrated  nitric 
acid.  Berthelot**  finds  it  to  be  acted  upon  by  fuming  hydro- 
chloric acid  in  the  presence  of  light  and  manganous  chloride. 
It  is  readily  soluble  in  aqua  regia.  Platinum  is  not  acted 
upon  by  sulphur  alone,  but  if  alkalies  are  present  with  the 
sulphur  some  action  takes  place.  It  is  attacked  also  when 
heated  with  potassium  nitrate.  Its  specific  gravity  is  2 1 .48. 

Besides  the  ordinary  form,  the  element  platinum  is 
known* to  exist  in  two  allotropic  conditions:  (i)  spongy 
platinum,  obtained  by  the  ignition  of  ammonium  chloro- 
platinate,  and  (2)  platinum-black,  obtained  by  reducing 
acid  solutions  of  platinum  salts.  In  both  of  these  forms 
platinum  condenses  gases  on  its  surf  ace.  ff 

Compounds.  A.  Typical  forms.  The  following  may  be 
regarded  as  typical  compounds  of  platinum: 

Oxides PtO  Pt304  Pt02  Pt03 

Chlorides PtCl2  PtCU  PtCl4 

Double  chlorides PtCl2  •  SrCl2-|-  PtCl4-  2AgCl,  etc. 

6H20,  etc. 

Bromides PtBr2  PtBr4 

Double  bromides PtBr2-  2KBr,  etc.  PtBr4-SrBr2+ioH2O 

*  Nernst,  Ber.  phys.  Ges.  rv,  48. 

t  U.  S.  Bureau  of  Standards  gives  1755°  C. 

J  Guntz,  Bull.  soc..chim.  [3]  xxxni,  1306. 

§  Moissan,  Compt.  rend.  CXLII,  189. 

I!  Quennessen,  Compt.  rend.  CXLII,  1341. 

1f  Marie,  Compt.  rend.  CXLVI,  475. 

**  Berthelot,  Compt.  rend,  cxxxvm,  1297. 

ft  Sieverts,  Ber.  Dtsch.  chem.  Ges.  XLV,  221;  Ztschr.  anorg.  Chem.  xcn,  329; 
Phillips,  Amer.  Chem.  J.  xvi,  163;  Paal,  Ber.  Dtsch.  chem.  Ges.  XLvrn,  1195, 
Curtman  and  Rothberg,  Jour.  Amer.  Chem.  Soc.  xxxra,  718. 


164  THE  RARER  ELEMENTS. 

Iodides  ...............  PtI2       &  ,   -        ^    ~      PtI4 

Double  iodides  ........  PtI4  •  aKI,  etc. 

Fluorides  ............  PtF,  PtF4 

Sulphides.  .  .  .  ........  PtS  PtS2 

Oxysulphide  ..........  PtOS 

Sulpho  salts  ..........  R2PtS6 

Sulphites  .............  PtS03  •  R2S03  ;  PtSO3  •  2RC1 

Nitrites  ..............  R2(NO,)4Pt 

lodonitrites  ..........  R2(NO2)2I2Pt 

Cyanide  ..............  Pt(CN), 

Hydro  -  platino  -  cyanic 
acid  ...............  H2Pt(CN)4 

Platino-cyanides  *  .....  R2Pt(CN)4;  RPt(CN)4,  typical 
Chloroplatinic  acid.  .  .. 


Chloroplatinates  t  .....  RzPtCU  ;  RPtCle,  typical 

Chloroplatinite  f  ......  K2PtCl4 

B.  Characteristics.  The  compounds  of  platinum  may 
be  divided  into  two  classes,  of  which  the  platinous  and 
platinic  oxides,  (PtO;  PtO2),  serve  as  types.  The  salts  of 
the  lower  condition  of  oxidation  are  usually  colorless  or 
reddish  brown;  they  give  with  hydrogen  sulphide  or  am- 
monium sulphide  a  dark-brown  precipitate  of  platinous 
sulphide,  (PtS),  which  is  soluble  in  ammonium  sulphide. 
They  are  decomposed  at  red  heat,  and  are  slowly  reduced 
to  metallic  platinum  when  boiled  with  ferrous  sulphate. 
The  salts  of  the  higher  condition  of  oxidation  have  a  yellow 
or  brown  color,  and  like  the  platinous  salts  they  are  de- 
composed at  red  heat.  Metals  in  general  and  organic 
matter  precipitate  platinum  from  solutions  of  platinic 
salts.  The  brownish-gray  platinic  sulphide,  (PtS2),  is  pre- 
cipitated by  the  action  of  hydrogen  sulphide  upon  a  solu- 
tion of  chloroplatinic  acid,  (H2PtCl6)  ;  this  sulphide  dissolves 
slowly  in  ammonium  sulphide.  Salts  of  potassium  and 
ammonium  act  upon  chloroplatinic  acid  precipitating  the 

*  Vid.  Tschugajew,  Ber.  Dtsch.  chem.  Ges.  XLVH,  2643. 
f  Vid.  Zappi,  Chem.  Abs.  x,  1307. 


PLATINUM.  Z65 

i 

corresponding  salts  of  that  acid,  (R2PtCl6) .  When  platinous 
chloride  dissolves  in  potassium  cyanide,  platinum  potas- 
sium cyanide  is  formed,  (K2Pt(CN)4+4H2O).  Many  salts 
of  this  type  are  known  (Levy,  Pro3.  Roy.  Soc.  xxvm,  91). 

The  platinum-ammonium  compounds  comprise  a  large 
number  of  complex  salts  *  of  the  following  types : 

(a)  The  platosamines,  PtR2(NH3)4;  PtR2(NH3)3; 
PtR2(NH3)2;  PtR2(NH3);  and  (6)  the  platinamines, 
PtR4(NH,)4;  PtR4(XH,)8;  PtR4(NH3)2;  PtR4(NH8). 

In  the  above  formulae  R  may  stand  for  OH,  Cl,  Br,  I, 
or  NO3.  These  compounds  are  formed  by  the  action  of 
ammonia  upon  the  platinum  salts. 

Potassium  iodide  gives  a  red-brown  color  to  very  dilute 
solutions  of  platinum  salts. 

Estimation.  A.  Gravimetric.  Platinum  is  generally 
weighed  as  the  metal,  obtained  (i)  by  precipitation  from 
solutions  of  ccmpounds  by  means  of  appropriate  reducing 
agents,  such  as  formic  acid,  alcohol  in  alkaline  solution,  or 
magnesium  (Atterberg,  Chem.  Ztg.  xxn,  538) ;  (2)  by  pre- 
cipitation of  the  sulphide  and  ignition;  (3)  by  precipitation 
of  ammonium  or  potassium  chloroplatinate,  and  decomposi- 
tion by  heat  into  the  metal  and  the  volatile  or  soluble 
alkali  chloride. 

B.  Volumetric.  Platinum  may  be  estimated  volumet- 
rically  by  reducing  the  tetrachlori.de  by  means  of  potas- 
sium iodide,  (PtCl4  +  4KI  =  PtI2  + 12  +  4KC 1) ,  and  determin- 
ing by  standard  sodium  thiosulphate  the  iodine  thus  liber- 
ated (Peterson,  Zeitsch.  anorg.  Chem.  xix,  59). 

Separation.  From  most  other  elements  platinum  may 
be  separated  by  the  action  of  reducing  agents  in  precipitat- 
ing the  metal  from  solutions.  From  the  metals  with  which 
it  is  most  often  found  associated  it  may  be  separated  by 

*  See  Werner,  Ber.  Dtsch.  chem.  Ges.  XL,  15;  Rosenheim,  Zeitsch.  anorg. 
Chem.  XLHI,  34;  Kirmreuther,  Ber.  Dtsch.  chem.  Ges.  XLIV,  3115;  Chugaev, 
Compt.  rend.  CLXII,  43. 


1 66  THE  RARER  ELEMENTS. 

the  following  methods:  from  gold  (i)  by  the  action  of 
ammonium  chloride  upon  the  chlorides,  ammonium  chloro- 
platinate  being  precipitated;  (2)  by  the  action  of  hydro- 
gen dioxide  and  sodium  hydroxide  upon  cold  solutions, 
the  gold  being  precipitated  (Vanino  and  Seeman,  Ber.  Dtsch. 
chem.  Ges.  xxxn,  1968) ;  (3)  by  the  action  of  oxalic  acid  or 
ferrous  salts,  gold  being  again  precipitated  (Hoffmann  and 
Kriiss,  Zeitsch.  anal.  Chem.  xxvn,  66;  Bettel,  Chem.  News 
LVI,  133);  from  silver  by  heating  the  metals  with  dilute 
sulphuric  acid,  silver  dissolving  (Steinmann,  Schweiz. 
Wchschr.  f.  Chem.  u.  Pharm.  XLIX,  441,  453) ;  from  mercury 
by  ignition  of  the  metals,  mercury  being  volatilized. 

The  separation  of  platinum  from  the  other  platinum 
metals  is  so  involved  with  the  separation  of  these  from 
each  other  that  the  whole  subject  will  be  briefly  considered 
in  this  place.  The  following  methods  have  been  suggested, 
(i)  The  ore  is  first  treated  with  chlorine  water,  which  ex- 
tracts the  gold,  then  with  dilute  aqua  regia,  which  dis- 
solves the  platinum,  palladium,  and  rhodium.  From  this 
solution  the  platinum  is  precipitated  by  ammonium  chloride 
and  alcohol;  and  from  the  filtrate,  after  neutralization  with 
sodium  carbonate,  the  palladium  is  precipitated  as  the 
cyanide  by  mercury  cyanide.  The  residue  from  the  aqua 
regia  treatment,  containing  osmium,  iridium,  and  ruthe- 
nium, is  heated  in  air.  Osmium  is  volatilized  as  the  tetrox- 
ide,  ruthenium  sublimes  as  the  dioxide,  and  iridium  is 
left  (Pirngruber,  J.  B.  (1888),  2560;  Wyatt,  Eng,  and  Min. 
J.  XLIV,  273).  (2)  A  neutral  or  acid  solution  of  the  plat- 
inum metals,  gold,  and  mercury,  containing  chlorine,  is 
treated  with  dilute  nitric  acid  and  heated  to  boiling  in  a 
retort ;  osmic  tetroxide  distils.  The  solution  is  cooled,  and 
shaken  with  ether,  which  withdraws  the  chloride  of  gold. 
After  the  removal  of  the  ether  and  gold  by  means  of  a 
separating  funnel  the  remaining  solution  is  treated  with 
ammonium  acetate  and.  boiled  with  formic  acid.  This 
treatment  precipitates  all  the  metals,  which  are  then  heated 


PLA  TINUM.  !67 

in  a  current  of  hydrogen  to  volatilize  the  mercury.  The 
remaining  metals  are  mixed  with  sodium  chloride  and 
heated  with  moist  chlorine,  and  the  mass  is  extracted  with 
water.  If  there  is  any  residue  at  this  point  it  will  probably 
be  found  to  be  indium  and  ruthenium.  The  solution  is 
treated  with  concentrated  ammonium  chloride  as  long  as 
any  precipitate  forms.  This  precipitate  consists  of  the 
double  chlorides  of  ammonium  with  platinum,  iridium,  and 
ruthenium  respectively,  palladium  and  rhodium  remaining 
m  solution.  The  precipitate  is  dissolved  in  warm  water 
and  treated  with  hydroxylamine,  which  reduces  the  irid- 
ium and  ruthenium  to  the  condition  of  the  sesquichlorides ; 
upon  the  addition  of  ammonium  chloride  platinum  is  pre- 
cipitated as  the  chloroplatinate.  The  hydroxylamine  fil- 
trate is  evaporated,  the  residue  is  heated  in  the  presence  of 
hydrogen  and  fused  with  potassium  hydroxide  and  nitrate, 
the  mass  is  cooled  and  extracted  with  water.  Ruthenium 
dissolves  as  potassium  ruthenate,  (K2RuO4),  and  iridium 
remains  as  the  hydrate,  (Ir(OH)3).  The  solution  contain- 
ing rhodium  and  palladium  is  evaporated  slowly  to  dryness 
in  the  presence  of  an  excess  of  ammonia,  and  the  residue 
is  dissolved  in  the  smallest  possible  amount  of  a  warm,  dilute 
ammoniacal  solution.  Upon  cooling,  the  rhodium  separates 
as  a  complex  chloride,  (Rh(NH3)5Cl3),  and  the  palladium 
remains  in  solution  (Mylius*  and  Dietz,  Ber.  Dtsch.  chem. 
Ges.  xxxi,  3187).  (3)  Gold  is  removed  by  means  of  dilute 
aqua  regia.  By  treatment  with  concentrated  aqua  regia 
platinum,  palladium,  rhodium,  ruthenium,  and  part  of  the 
iridium  are  then  dissolved,  while  an  insoluble  alloy  of  os- 
mium and  iridium  in  the  form  of  grains  or  plates  remains. 
This  alloy  is  mixed  with  sodium  chloride  and  the  mixture 
is  heated  in  a  tube  with  chlorine.  Osmium  tetroxide, 
(OsO4),  distils,  and  sodium-iridium  chloride,  (Na2IrCl6),  re- 
mains (Wohler,  Pogg.  Annal.  xxxi,  161).  To  the  solution  of 

*  Vid.  also  Mylius  and  Mazzucchelli,  Ztschr.  anorg.  Chem.  LXXXIX,  i;   Korf- 
man,  Chem.  Abs.  ix,  2629. 


168  THE  RARER  ELEMENTS. 

the  other  platinum  metals  in  aqua  regia  ammonium  chloride 
is  added.  The  precipitate,  consisting  of  the  double  salts  of 
platinum  and  iridium,  may  by  ignition  be  converted  intc 
indium-bearing  platinum  sponge  (used  in  the  manufacture 
of  platinum  vessels) .  To  the  nitrate  iron  or  copper  is  added, 
which  throws  down  the  palladium,  rhodium,  and  ruthenium 
as  a  metallic  powder.  From  this  mixture  palladium  and 
the  iron  or  copper  are  dissolved  by  nitric  acid,  and  the  solu- 
tion is  then  shaken  with  mercury,  which  removes  the  palla- 
dium (von  Schneider,  Liebig  Annal.  v,  264,  suppl.).  The 
mixture  of  rhodium  and  ruthenium  remaining  is  heated  with 
sodium  chloride  at  low  redness  in  a  current  of  chlorine  and 
the  mass  is  extracted  with  water.  This  liquid  is  boiled 
with  potassium  nitrite  and  enough  potassium  carbonate 
to  make  the  solution  faintly  alkaline.  It  is  then  evaporated 
to  dryness  and  the  residue  is  pulverized  and  extracted 
with  absolute  alcohol.  The  rhodium  remains  undissolved 
as  a  double  nitrite  of  potassium  and  rhodium,  (K6Rh2(NO2)12, 
while  the  ruthenium  dissolves,  also  as  a  double  nitrite  with 
potassium,  (Ru(NO2)6-6KNO2). 

Platinum  may  be  separated  from  palladium  (i)  by  the 
.action  of  warm  dilute  nitric  acid  upon  the  metals,  palladium 
dissolving;  (2)  by  the  action  of  a  strong  solution  of  am- 
monium chloride  and  alcohol  upon  the  double  potassium 
salts,  the  palladium  salt  being  soluble  (Cohn  and  Fleissner, 
Ber.  Dtsch.  chem.  Ges.  xxix,  R.  876);  from  iridium  (i)  by 
electrolysis,  the  platinum  being  precipitated  (Smith,  Amer. 
Chem.  Jour,  xiv,  435) ;  (2)  by  the  action  of  potassium 
nitrite,  sodium  carbonate,  and  boiling  water  upon  the 
double  potassium  salts,  iridium  being  reduced  to  the  con- 
dition of  the  sesquichloride  and  dissolved  (Gibbs,  Amer. 
Jour.  Sci.  [2]  xxxiv,  347) ;  from  osmium  by  heating  in  the 
presence  of  oxidizing  material,  osmium  tetroxide  being 
formed  and  volatilized;  from  ruthenium  by  treating  potas- 
sium chloroplatinate  and  the  corresponding  ruthenium 
salt  with  cold  water,  the  ruthenium  salt  dissolving  (Gibbs, 


EXPERIMENTAL   WORK  ON  PLATINUM.    '  169 

loc.  cit.) ;  from  rhodium  (i)  by  the  method  described  for 
the  separation  from  ruthenium;  or  (2)  by  the  action  of 
concentrated  solutions  of  the  alkali  chlorides  upon  these 
salts,  the  rhodium  dissolving  (Gibbs,  loc.  cit.). 

A  method  of  separation  proposed  by  Leidie  and  Quen- 
nessen  (Bull.  Soc.  Chim.  xxvn,  (1902)  181),  will  be  found 
outlined  in  Table  IX,  page  226. 

EXPERIMENTAL  WORK  ON  PLATINUM. 

Experiment  i.  Preparation  of  chloroplatinic  acid  from 
laboratory  residues.  Boil  the  residues  consisting  of  potas- 
sium chloroplatinate,  etc.,  with  a  solution  of  sodium  car- 
bonate and  add  a  little  formic  acid  or  formate  in  solution. 
The  platinum  is  deposited  as  a  black  powder.  Wash  the 
powder,  first  with  hot  water,  then  with  hot  hydrochloric 
acid;  dry  it,  dissolve  it  in  aqua  regia,  and  evaporate  the 
liquid  until  the  point  of  crystallization  is  reached,  adding 
a  little  hydrochloric  acid  from  time  to  time  to  remove  the 
nitric  acid,  and  some  chlorine  water  to  convert  any  platinous 
acid  to  the  platinic  condition. 

Experiment  2.  Precipitation  of  the  chloroplatinates 
of  ammonium,  potassium,  ccesium,  rubidium,  and  thallium, 

(R^PtCle).  To  separate  portions  of  a  solution  of  chloro- 
platinic acid  add  salts  of  ammonium,  potassium,  caesium, 
rubidium,  and  thallium  in  solution.  Note  the  comparative 
insolubility  of  the  new  compounds  in  water  and  in  alcohol. 

Experiment  3.  Formation  of  chloro platinous  acid.  To  a 
solution  of  chloroplatinic  acid  add  a  little  stannous  chloride. 
Note  the  darkening  of  the  color.  Add  a  little  potassium  or 
ammonium  salt  in  solution.  Note  the  absence  of  pre- 
cipitation. 

Experiment  4.  Precipitation  of  platinic  sulphide,  (PtS2). 
To  a  solution  of  chloroplatinic  acid  add  a  little  hydrogen  sul- 
phide, and  warm.  Try  action  of  ammonium  sulphide  on  PtS2- 

Experiment  5.     Precipitation    of   elementary    platinum. 


170  THE  RARER  ELEMENTS. 

(a)  To  a  solution  of  a  platinum  salt  add  a  few  drops  of  a 
solution  of  hydrazine  sulphate  (N2H4-H2SO4)  and  warm. 

(b)  Try  the   action   of  zinc  on   a   solution  containing 
platinum. 

(c)  Try  the  action  of  oxalic  acid  upon  a  platinum  salt 
in  solution.     Note  the  absence  of  precipitation. 

Experiment  6.  Action  of  acids  upon  platinum.  Try 
separately  the  action  of  strong  hydrochloric  and  nitric 
acids  upon  metallic  platinum.  Note  the  effect  of  a  mixture 
of  the  two  acids  upon  the  metal. 

Experiment  7.  Test  for  platinum  in  solution.  To  a  very 
dilute  solution  of  a  platinum  salt  free  from  chlorine  add  a 
small  crystal  of  potassium  iodide.  Note  the  color. 

Experiment  8.  "  Glow  test  "for  platinum.*  Dip  the  end 
of  a  very  small  piece  of  asbestos  paper  into  i  cm.3  of  chloro- 
platinic  acid,  heat  the  asbestos  to  redness,  and  repeat  the 
process  until  the  liquid  is  completely  absorbed.  Then, 
before  the  asbestos  cools,  hold  it  in  a  current  of  illuminating 
gas. 

THE  PLATINUM  METALS  (OTHER  THAN  PLATINUM). 

Occurring  almost  invariably  associated  with  platinum 
and  usually  alloyed  with  it  are  small  quantities  of  certain 
rare  elements  which,  together  with  platinum,  comprise 
the  group  of  so-called  Platinum  Metals.  These  very  rare 
elements  are  the  following: 

Palladium,  Pd,  106.7  Osmium,  Os,  190.9 

Iridium,  Ir,  193.1  Rhodium,  Rh,  102.9 

Ruthenium,  Ru,   101.7 

Discovery.  In  1803,  in  the  course  of  the  purification 
of  a  considerable  quantity  of  crude  platinum,  Wollaston 

*  This  test  applies  also  to  Pd,  Ir,  and  Rh.  It  is  stated  that  under  proper  con- 
ditions .002  mg.  of  Pt  can  be  detected  (Curtman  and  Rothberg,  Jour.  Amer.  Chem. 
Soc.  xxxra,  718). 


THE  PLATINUM  METALS.  I7x 

I 

isolated  a  new  metal  which  he  named  Palladium,  in  honor 
of  the  discovery  by  Olbers  of  the  planetoid  Pallas.  The  newly 
discovered  element  was  brought  to  the  attention  of  scien- 
tists anonymously  through  a  dealer's  advertisement,  which 
offered  "palladium  or  new  silver"  for  sale.  Much  dis- 
cussion as  to  the  nature  of  the  substance  ensued,  Chenevix, 
in  particular,  holding  it  to  be  an  alloy  of  platinum  and  mer- 
cury. In  1805  Wollaston  confessed  to  the  discovery  and 
naming  of  the  metal  (Phil.  Trans.  Roy.  Soc.  (1803)  xcm, 
290;  ibid.  (1805)  xcv,  316;  Nicholson's  J.  (1805)  x,  204). 

The  same  year  that  palladium  was  discovered,  Smithson 
Tennant  found  that ' '  the  black  powder  which  remained  after 
the  solution  of  platina  did  not,  as  was  generally  believed, 
consist  chiefly  of  plumbago,  but  contained  some  unknown 
metallic  ingredients."  In  1804  he  presented  to  the  Royal 
Society  as  the  result  of  his  study  a  communication  announc- 
ing the  discovery  of  two  new  metals,  Iridium,  named  "from 
the  striking  variety  of  colors  which  it  gives  while  dissolving 
in  marine  acid,"  and  Osmium,  so  called  because  of  the 
penetrating  odor  (007/77,  odor]  of  the  acid  obtained  from 
the  oxidation  of  the  element  when  it  is  heated  in  a  finely 
divided  condition  (Phil.  Trans.  Roy.  Soc.  (1804)  xciv,  411). 

A  few  days  after  Tennant 's  communication,  Wollaston 
announced  the  discovery  of  an  element  in  the  ' '  fluid  which 
remains  after  the  precipitation  of  platina  by  sal  ammoniac, ' ' 
and  suggested  the  name  Rhodium  (podios,  rose-like],  "from 
the  rose  color  of  a  dilute  solution  of  the  salts  containing 
it"  (Phil.  Trans.  Roy.  Soc.  (1804)  xciv,  419). 

In  1826  Osann  claimed  the  discovery  of  three  new  ele- 
ments in  platinum  alloys.  These  he  named  Ruthenium, 
Polinium,  and  Pluranium  (Pogg.  Annal.  vm,  505 ;  Amer. 
Jour.  Sci.  xvi,  384).  Later  he  withdrew  the  claim.  In 
1844  Claus  found  that  there  was  an  unknown  metal  in  the 
mixture  of  substances  which  had  been  called  by  Osann 
"ruthenium  oxide,"  and  for  it  he  retained  the  name 
ruthenium,  derived  from  Ruthenia,  i.e.  Russia,  where  the.. 


172  THE  RARER  ELEMENTS. 

substance  was  first  found  (Pogg.  Annal.  LXIV,  192,  208; 
Amer.  Jour.  Sci.  XLVIII,  401). 

Late  in  the  year  1911  French  (Chem.  News  civ,  283) 
announced  the  discovery  of  an  element  associated  with 
the  platinum  metals  in  the  dike  rocks  of  the  Nelson  dis- 
trict in  British  Columbia.  It  had  the  characteristics  of  a 
noble  metal  and  was  called  by  him  Canadium.  Patterson 
(Chem.  News  cv,  84),  in  discussing  this  discovery,  calls 
attention  to  the  fact  that  palladium  forms  alloys  with  many 
metals,  and  that  these  alloys  behave  very  differently  from 
palladium  and  resemble  elementary  substances. 

Occurrence.  The  very  rare  platinum  metals,  as  has 
been  already  stated,  are  found  in  general  in  platinum- 
bearing  material.  Palladium  and  iridium  sometimes  occur 
native;  the  others  always  in  alloys  or  in  combination. 

#Pd  *Os  *Ir  #Rh  %  Ru 

Native  platinum  contains  0.1-3.1  traces-4 . 2       traces          o .  2-3 . 4 

iridium  0.4-0.8  27-76.8  circa-] 

Palladium  gold  5-10 

Iridosmine 
Laurite,  RuS3 
Rhodium  gold 


17-48  40.7      9.5-12.3  0.2-6 

circa  3  65 

34-43 


Extraction.  For  methods  of  extraction  of  the  very 
rare  platinum  metals  see  Extraction  and  Separation  of 
Platinum. 

The  Elements.  I.  PALLADIUM.  A.  Preparation.  Ele- 
mentary palladium  may  be  obtained  (i)  by  heating  the 
potassium  double  chloride  with  hydrogen  (Roessler) ;  (2)  by 
heating  the  iodide  with  hydrogen;  and  (3)  by  heating  the 
chloride  or  cyanide. 

B.  Properties.  Palladium  is  a  ductile,  malleable,  white 
metal  which  looks  like  platinum.  It  may  be  partially 
oxidized  before  the  oxyhydrogen  blowpipe.  It  is  soluble 
in  strong  nitric,  hydrochloric,  and  sulphuric  acids,  and 
easily  soluble  in  aqua  regia.  It  fuses  at  a  lower  temperature 
than  any  other  of  the  platinum  metals,  1549°  C.  (U.  S. 
Bureau  of  Standards).  In  spongy  form  it  has  the  power  of 


THE   PLATINUM   METALS.  175 

absorbing  gases.*  Its  specific  gravity  is  11.4-11.8.  It  may 
be  distinguished  from  the  other  platinum  metals  by  the 
comparative  ease  with  which  it  dissolves  in  nitric  acid. 

II.  OSMIUM.      A.  Preparation.      The    element   osmium 
may  be  prepared  (i)  by  heating  the  amalgam  in  the  presence 
of  hydrogen  (Berzelius) ;  (2)  by  heating  the  sulphide  in  a 
closed  coke  crucible ;  (3)  by  passing  the  vapor  of  the  tetroxide 
mixed  with  carbon  dioxide  and  carbon  monoxide  through  a 
heated  porcelain  tube;   (4)   by  passing  the  vapor  of  the 
tetroxide  through  a  heated  porcelain  tube  containing  finely 
divided   carbon    (Deville    and    Debrayj ;    (5)    by    igniting 
osmyldiamine   chloride,    (Os(NH3)4O2CL),  in   a   current   of 
hydrogen. 

B.  Properties.  Osmium,  the  heaviest  of  the  platinum 
metals,  is  a  bluish  substance,  crystals  of  which  are  harder 
than  glass.  In  the  compact  form  it  is  insoluble  in  all  acids 
and  in  aqua  regia,  and  is  rendered  soluble  only  by  fusion 
with  nitrates.  The  amorphous  modification  is  slowly  soluble 
in  nitric  acid  and  in  aqua  regia.  The  specific  gravity  of  the 
compact  and  amorphous  modifications  is  2 1 .3  ;  of  the  crystal- 
line form  22.4.  Osmium,  like  the  other  platinum  metals,  has 
been  volatilized  in  the  electric  furnace  (Moissan.Compt.rend. 
CXLII,  189) ;  it  is,  however,  refractory,  f  Its  melting-point  is 
2700°  C. 

III.  IRIDIUM.     A.  Preparation.     Metallic  iridium  may 
be  obtained   (i)   by  heating  indium-ammonium  chloride, 
and  (2)  by  heating  indium-potassium  chloride  with  sodium 
carbonate. 

B.  Properties.     Iridium,  a  hard,  brittle  metal,  resembles 

*  The  explosive  condition  of  the  platinum  metals  is  explained  by  the  property, 
common  to  these  metals,  of  occluding  hydrogen  and  oxygen.  When  heated  in 
nitrogen  or  out  of  contact  with  the  air  they  tend  to  lose  their  explosive  character. 
Ruthenium,  however,  is  not  changed  by  this  treatment  (Cohen  and  Strengers, 
Z.  physik.  Chem.  LXI,  698).  Vid.  also  Sieverts,  ibid.  LXXXVIII,  451;  Halla,  ibid. 
LXXXVI,  496;  Curtman  and  Rothberg,  Jour.  Amer.  Chem.  Soc.  xxxni,  718. 

t  For  a  discussion  of  the  volatility  of  the  platinum  metals,  see  Crookes,  Proc. 
Roy.  Soc.  LXXXVI,  461. 


I74  THE  RARER  ELEMENTS. 

silver  ancftin  in  appearance.  The  ignited  form  is  insoluble 
in  all  acids  and  in  aqua  regia.  The  element  is  partially 
oxidized,  however,  by  fusion  with  sodium  nitrate,  and  the 
fused  mass  may  be  dissolved  by  boiling  it  with  aqua  regia. 
In  spongy  form  iridium  has  the  specific  gravity  of  15.86; 
after  fusion  the  specific  gravity  is  21-22.  It  has  the  prop- 
erty of  absorbing  gases.* 

IV.  RHODIUM.     A.  Preparation.      Elementary  rhodium 
may  be  prepared  (i)  by  heating  ammonium -rhodium  ses- 
quichloride;    (2)    by  heating  rhodium   sesquichloride   and 
sodium  in  a  current  of  hydrogen;  (3)  by  heating  rhodium 
sulphide  to  a  white  heat;   and  (4)  by  allowing  reducing 
agents,  as  formic  acid,  zinc,  iron,  alcohol  in  alkaline  solu- 
tion, hydrogen,  etc.,  to  act  upon  soluble  salts. 

B.  Properties.  Rhodium  is  a  grayish-white  metal  which 
has  the  appearance  of  aluminum.  When  pure  it  is  almost 
absolutely  insoluble  in  acids  and  in  aqua  regia,  but  when 
alloyed  it  may  be  dissolved  in  aqua  regia.  It  -is  fusible 
before  the  oxyhydrogen  blowpipe,  but  more  difficultly 
than  platinum.  It  has  the  property  of  absorbing  hydrogen.  * 
Of  all  the  platinum  metals  rhodium  is  most  easily  attacked 
by  chlorine.  Its  specific  gravity  is  11-12.  Its  melting-point 
is  1950°  C. 

V.  RUTHENIUM.    A.    Preparation.    The  element  ruthe- 
nium may  be  obtained  (i)  by  heating  the  oxide  with  illu- 
minating-gas,  and   (2)   by  heating  ruthenium-ammonium- 
mercury  chloride. 

B.  Properties.  Ruthenium  is  a  hard,  brittle  metal,  dark 
gray  to  black  in  color.  It  is  almost  completely  insolu- 
ble in  acids  and  in  aqua  regia;  and  osmium  alone,  of  all 
the  platinum  metals,  is  more  difficultly  fusible.  It  may 
be  slightly  oxidized  by  fusion  with  caustic  potash  and 
oxidized  to  a  greater  degree  by  fusion  with  potassium 
nitrate.  The  specific  gravity  of  the  crystalline  form  is 

*  See  Curtman  and  Rothberg,  Jour.  Amer.  Cheru.  Soc.  xxxiu,  718. 


THE  PLATINUM  METALS. 


175 


12.26;  of  the  melted  form  11.4;  and  of  the  porous  form  8.6. 
Its  melting-point  is  2450°  C.  ? 

Compounds.*    A.  Typical  forms.    The   following   com- 
pounds of  the  platinum  metals  may  be  considered  typical : 


Oxides Pd2O 

PdO 

Pd203t 

PdO, 


Chlorides PdCl 

PdCl, 

PdCl4 
Bromides PdBr, 

PdBr4 
Iodides Pdl, 


Sulphides Pd2S 

PdS 

PdS, 
Sulphates PdSO4 


OsO 


Os02 

(OsO,)t 

OsO« 


OsCl2 
OsCl3 
OsCl4 


OsS2 
OsS4 


IrO? 
Ir:O, 
IrO?f 


IrCl2 
IrCl4 

Ir2Br, 
IrBr4 

IrA? 

IrI4 

IrS 

Ir2S, 

IrS2 

Ir2(S04)3  § 


Sulphites PdSOj-          OsSO, 


RhO 

Rh20s 

RhO, 


RhCl, 
Rh2Cl, 


Rh2Ia 


RhS 
Rh2S, 


Rh2(SO<)3 


Rh,(SO,), 


RuO 

Ru2O3 

RuO, 

(RuO3)  t 
RuO4 

(Ru2O7) 

RuCl2 
RU.C1, 
RuCl, 


Ru2I8 


Ru:S3 
RuS2 
RuS3 


*  Gutbier,  Ber.  Dtsch.  chem.  Ges.  XLIII,  3228,  3234;  XLIV,  306,  308;  XLVII, 
236;  J-  prakt.  Chem.  xci,  103;  Delepine,  Compt.  rend.  CLVHI,  264;  Fritzman,  J. 
Russ.  Phys.  Chem.  Soc.  XLVII,  588;  Peters,  Ztschr.  anorg.  Chem.  LXXXIX,  191; 
Tschugajew,  Ber.  Dtsch.  chem.  Ges.  XLVII,  2446;  Gutbier,  Ztschr.  anorg.  Chem. 
xxxxrx,  313,  333,  340,  344;  Barbieri,  Atti  R.  Accad.  dei  Lincei,  Roma  [5]  xxm, 
I,  334;  Fraenkel,  Monatshefte  Chem.  xxxv,  19;  Ramberg,  Ber.  Dtsch.  chem. 
•Ges.  XLVI,  1696,  3886;  Wohler,  Ber.  Dtsch.  chem.  Ges.  XLVI,  1577,  1591,  1720; 
Ruff,  ibid.  XLVI,  920. 

t  Wohler,  Zeitsch.  anorg.  Chem.  LVH,  323,  398. 

t  This  oxide  is  known  only  in  combination. 

§  Also  alums,  see  Marino,  Zeitsch.  anorg.  Chem.  XLH,  213;  complex  oxalates, 
see  Gialdini,  Atti  R.  Accad.  dei  Lincei,  Roma  [5]  xvi  [n],  648,  or  Chem.  Zentr. 
<i9o8)  I,  107.  . 


176  THE  RARER  ELEMENTS. 

Sulpho  salts.... R2Pd3S4 
R2PdS3 

Nitrites Pd(NO,)2-  2KNO2 

Os(N(V,*    Ir,(NO,\.      Rh,(NO2V      Ru2(NO;)« 
6HNO,  6RN02  6RNO2 

Nitrates PdCNO^ 

Rh2(NCgu 
Acids  and  corre- 

spond'g  salts...  H2PdCl,;t 
R2PdCl, 

H3OsCl«;  R.RhCl,;         H,RuClji 

R3OsCl4  R3RhCl,  § 

H2PdCl8;       H2OsCl0;  H2RuCl6 

R2PdCl0          R2OEC1,      RjIrCl, 

Characteristics.  I.  PALLADIUM.  The  compounds  of  pal- 
ladium resemble  those  of  platinum,  both  in  form  and 
in  general  characteristics.  As  in  the  case  of  platinum, 
palladium  combines  with  ammonia  to  form  complex  salts, 
and  an  oxide,  (PdO),  forms  salts  with  sulphur  dioxide  and 
with  nitrogen  trioxide,  (N2O3).  In  general  the  salts  are 
quite  easily  reduced  to  the  metal  by  heating ;  their  solutions 
resemble  a .  solution  of  platinic  chloride  in  color.  Two 
oxides,  (PdO;  PdO2),  are  well  known,  of  which  the  lower 
forms  the  more  stable  compounds.  These  compounds  give 
a  yellowish-brown  precipitate  with  potassium  hydroxide. 
Solutions  of  palladium  salts  give  with  mercuric  cyanide  a 
yellowish- white  precipitate,  (Pd(CN)2) ;  with  potassium 
iodide  a  black  precipitate,  (PdI2),  which  is  soluble  in  excess 
of  the  reagent ;  and  with  hydrogen  sulphide  also  a  black 
precipitate,  (PdS),  insoluble  in  ammonium  sulphide. 

*  See  also  Wintrebert,  Compt.  rend.  CXL,  585. 

f  See  also  Gutbier,  Ber.  Dtsch.  chem.  Ges.  xxxvm,  23;  xxxix,  4134;  XL, 
690;  Zeitsch.  anorg.  Chem.  XLV,  166,  243;  XLVII,  23. 

t  See  also  Howe,  Jour.  Amer.  Chem.  Soc.  xxvi,  543,  942;  Gutbier,  Zeitsch. 
anorg.  Chem.  XLV,  166,  243;  XLVII,  23;  Ber.  Dtsch.  chem.  Ges.  xxxvm,  2105, 
2885. 

§  See  also  Gutbier,  Ber.  Dtsch.  chem.  Ges.  XLI,  210. 


THE  PLATINUM  METALS.  177 

Mercuric  cyanide  and  potassium  iodide  are  often  used  as: 
tests  for  palladium. 

II.  OSMIUM.*   Compounds  of  osmium  are  known  in  five' 
degrees    of    oxidation.     The    lowest    three    oxides,    (OsO;; 
Os2O3;  OsO2),  are  basic  in  character,  the  fourth,  f  (OsO3), 
is  acidic,  and  the  fifth,  (OsO4),  is  also  acidic,  but  it  forms 
no  salts.     Three  chlorides,  (OsCl2;  OsQ3;  OsClJ,  are  known,. 

corresponding  to  the  lowest  oxides.     The  metals  sodium^. 

i 

potassium,  and  barium  form  salts  of  the  type  R2OsO4.. 
These  salts  are  readily  decomposed,  especially  by  acids,  and. 
form  the  dioxide  and  the  tetroxide.  When  osmium  com- 
pounds are  heated  in  the  air  with  oxidizing  agents,  or  are 
melted  with  potassium  nitrate,  the  tetroxide  is  obtained. 
It  is  volatile  when  heated,  highly  corrosive,  and  disagree- 
able like  chlorine.  It  is  soluble  in  water  and  is  reduced 
by  reducing  agents.  From  potassium  iodide  it  frees  iodine, 
and  with  formic  acid  to  which  potassium  hydroxide  has 
been  added  it  gives  a  violet  color.  With  ferrous  sulphate 
it  precipitates  black  osmium  hydroxide,  (Os(OH)4\  and 
with  hydrogen  sulphide  it  brings  down  the  brownish-black 
sulphide  (OsS4),  which  is  insoluble  in  ammonium  sulphide. 

III.  IRIDIUM.  J     The  compounds  of  iridium  exist  chiefly 
in  three  conditions  of  oxidation,  of  which  the  di-,  tri-,  and 
tetrachlorides    may    serve    as    types,   (IrCl2;  Ir2Cl6;  IrCI4). 
The  iridium  compounds  are  reduced  to  the  metal  when 
mixed  with   sodium   carbonate   and   heated   in   the   outer 
flame  of   a   Bunsen  burner.     The  alkali  double  chlorides 
with  iridous  chloride,  (IrCl,),  are  in  general  soluble  in  water. 
Solutions  of  iridium  salts  in  the  lowest  condition  of  oxida- 
tion give  with  potassium  hydroxide  a  greenish  precipitate, 

*  See  also  Ruff,  Zeitsch.  anorg.  Chem.  LXV,  429;  Gutbier,  Ber.  Dtsch.  chem. 
Ges.  XLIII,  3228,  3234;  XLIV,  306,  308. 

t  Known  only  in  salts. 

J  For  recent  work  on  iridium  compounds  see  Gutbier,  Ber.  Dtsch.  chem.  Ges. 
XLII,  3905,  4770;  Delepine,  Vezes  and  Duffour,  Bull.  Soc.  Chim.  [4],v,  869,  872,, 
1084;  vn,  507,  512;  DC,  710,  771;  Compt.  rend,  cm,  1393,  1591. 


178  THE  RARER  ELEMENTS. 

Miich  tends  to  darken  when  boiled.  Reducing  agents, 
as  sodium  formate,  precipitate  metallic  indium,  and  hydro- 
gen sulphide  precipitates  from  the  warmed  solution  a  brown 
iridium  sulphide  (IrS).  By  means  of  oxidizing  agents, 
solutions  of  iridous  salts  may  be  converted  into  the  high- 
est condition  of  oxidation.  From  solutions  of  this  latter 
type  potassium  hydroxide  throws  down  a  dark-brown  pre- 
•cipitate  of  potassium -iridium  chloride,  (IrCl4-2KCl),  and 
-hydrogen  sulphide  precipitates  slowly  a  brown  sulphide, 
(Ir2S3).  The  greater  number  of  iridium  compounds  are 
easily  reduced  by  hydrogen  on  being  heated.  The  pres- 
ence of  indium  may  be  detected  by  the  blue  color  de- 
veloped when  the  compound  is  heated  with  concentrated 
sulphuric  acid  to  which  ammonium  nitrate  has  been  added. 

IV.  RHODIUM.     Although  three  oxides  of  rhodium  are 
known  and  described,  (RhO;  Rh2O3;  RhO2),  salts  of  only 
two  conditions  of  oxidation  are  generally  found;  of  these 
the  di-  and  trichlorides  are  types,  (RhCl2;  Rh2Cl6).     From 
solutions  of  rhodium  salts  reducing  agents  precipitate  the 
metal.     Hydrogen  sulphide  throws  down  from  a  cold  solu- 
tion the   sulphide   (Rh2S3),  and  from  a  hot  solution  the 
sulphydrate   (Rh2(SH)6).     The  insolubility  of  the   double 
chloride  of  rhodium  and  sodium,  (Rh2Cl'6NaCl),  in  water, 
and  of   the   double   nitrate   c-f  rhodium   and   potassium, 
(K6Rh6(NO2)12),  in  alcohol  is  made  use  of  in  separating  the 
metal  from  the  other  members  of  the  group.     Rhodium 
is  detected  in  the  presence  of  the  other  platinum  metals  by 
the  yellow  solution  obtained  after  fusion  with  potassium 
acid  sulphate  and  the  change  of  color  to  red  upon  the  ap- 
plication of  hydrochloric  acid. 

V.  RUTHENIUM.     In  the  variety  of  conditions  of  oxida- 
tion in  which  they  are  found,  the  compounds  of  ruthenium 
resemble  those  of  osmium.     The  lowest  three  oxides  are 
basic  in  character,  (RuO ;  Ru2O3 ;  RuO2) ,  and  form  salts  of 
which  the  three  chlorides,  (RuCl2 ;  Ru2Cl6 ;  RuCl4),are  typical. 
The  trioxide,  (RuO3),  is  known  only  in  combination,  where 


THE  PLATINUM  METALS. 


179 


it  acts  as  an  acid  and  forms  salts  of  the  type  RsRuO,. 
Another  oxide,  (Ru2O7),  known  only  in  combination,  forms 

i 

salts  represented  by  the  formula  RRuO4.  The  tetroxide 
(RuO4)  is  volatile  and  similar  to  the  corresponding  oxide  of 
osmium  in  its  chemical  behavior;  it  has  a  characteristic 
odor.  A  solution  of  the  trichloride,  (Ru2Cl6),  throws  out, 
when  heated,  a  dark  precipitate  which  is  generally  sup- 
posed to  be  an  oxychloride;  this  precipitate  is  held  in 
suspension  in  the  liquid  and  gives  a  pronounced  coloration, 
even  in  very  dilute  solutions.  Hydrogen  sulphide,  acting 
upon  solutions  of  ruthenium  salts,  precipitates  a  mixture 
of  sulphides,  oxysulphides,  and  sulphur;  this  mixture  is 
brown  or  black,  and  may  contain  one  or  more  of  the  sul- 
phides Ru2S3,  RuS,,  and  RuS3. 

Estimation.  The  platinum  metals  are  weighed  in  the 
elementary  condition,  obtained  as  described  under  Prepara- 
tion of  the  various  metals. 

Osmium  may  be  determined  volumetrically  by  causing 
potassium  iodide  to  act  upon  the  tetroxide  in  the  presence 
of  dilute  sulphuric  acid,  (OsO4  +  4KI  + 2H2SO4  =Os02  + 
2K,SO4  +  4l  +  2H2O),  and  estimating  by  means  of  sodium 
thiosulphate  the  iodine  thus  liberated  (Klobbie,  Chem. 
Central-Blatt  (1898)  n,  65  (abstract).  The  gravimetric 
methods  for  the  determination  of  osmium  have  recently 
been  studied  by  Paal  (Ber.  Dtsch.  chem.  Ges.  XL,  1378) 
and  found  unsatisfactory. 

Separation.  The  separation  of  the  platinum  metals 
has  been  considered  under  Platinum.  The  following  are 
additional  references:  Gibbs,  Amer,  Jour.  Sci.  [2]  xxxi,  63; 
xxxiv,  341;  xxxvu,  57;  Forster,  Zeitsch.  anal.  Chem. 
v,  117;  Bunsen,  Liebig  Annal.  CXLVI,  265;  Chem.  News 
xxi,  39;  Deville  and  Debray,  Compt.  rend.  LXXXVII,  441; 
Chem.  News  xxxvm,  188;  Wilm,  Ber.  Dtsch.  chem.  Ges. 
xvi,  1524;  Leidie,  Compt.  rend,  cxxxi,  888;  Bull.  Soc. 
Chim.  d.  Paris  [3]  xxvn,  179;  Bannister,  Analyst,  xxxix, 
340;  Wunder,  Ztschr.  anal.  Chem.  LII,  660,  740. 


i8o  THE  RARER  ELEMENTS. 


EXPERIMENTAL  WORK  ON  THE  PLATINUM 
METALS. 

Experiment  i.  Precipitation  of  palladous  iodide,  (PdI2). 
To  a  solution  of  a  palladium  salt  add  a  little  potassium 
iodide  in  solution. 

Experiment  2.  Precipitation  of  palladous  sulphide, 
(PdS).  (a)  Pass  hydrogen  sulphide  through  a  solution  of 
a,  palladous  salt. 

(6)  Try  the  action  of  ammonium  sulphide  upon  a  palla- 
•dous  salt  in  solution. 

Experiment  3.  Precipitation  of  the  hydroxide  or  basic 
salt.  To  a  solution  of  a  palladous  salt  add  a  little  sodium 
'hydroxide  or  carbonate  in  solution. 

Experiment  4.  Precipitation  of  palladous  cyanide.  To 
a  solution  of  a  palladous  salt  add  a  sohition  of  mercuric 
cyanide.  Try  the  action  of  potassium  cyanide  and  ammo- 
nium hydroxide  upon  the  precipitate. 

Experiment  5.  Action  of  ammonium  chloride  upon 
palladous  aud  palladia  chlorides.  (a)  To  a  solution  of 
palladous  chloride  add  ammonium  chloride. 

(b)  Saturate  a  solution  of  palladous  chloride  with 
chlorine  and  add  ammonium  chloride.  The  palladic  salt 
(PdCl6)(NH4)2  is  insoluble. 

Experiment  6.  Precipitation  of  the  nitroso-(3-naphthol  salt, 
(Pd(CioH6NO2)2.*  To  a  solution  of  a  palladous  salt  add 
a  saturated  solution  of  nitroso-jS-naphthol  in  50%  acetic 
acid. 

Experiment  7.  Precipitation  of  elementary  palladium. 
(a)  To  a  solution  of  a  palladium  salt  add  sodium  carbonate 
to  alkaline  reaction  and  a  little  formic  acid,  and  warm. 
(6)  Try  the  action  of  zinc  and  hydrochloric  acid,  f 

*  Wunder,  Ztschr.  anal.  Chem.  m,  737. 

f  Sulphurous  acid,  cuprous  chloride,  and  ferrous  sulphate  will  also  reduce  to 
.the  metal. 


EXPERIMENTAL  WORK  ON  THE  PLATINUM  METALS.       181 

Experiment  8.  Precipitation  of  osmium  sulphide,  (OsS4). 
(a)  To  a  solution  of  osmium  tetroxide  acidified  with  hydro- 
chloric acid  add  a  little  hydrogen  sulphide. 

(6)  Try  the  action  of  ammonium  sulphide  upon  the 
tetroxide  in  solution. 

Experiment  9 .  Formation  of  potassium  osmate,  (K2OsO4) . 
To  a  solution  of  osmium  tetroxide  add  a  solution  of  potas- 
sium hydroxide.  Note  the  yellow  color. 

Experiment  10.  Action  of  reducing  agents  upon  osmium 
tetroxide.  Try  the  action  of  an  alkali  sulphite,  formic  acid, 
and  tannic  acid,  respectively,  upon  a  solution  of  osmium 
tetroxide. 

Experiment  u.  Color  test  for  osmium.  To  a  solution  of 
osmium  tetroxide  or  any  other  compound  of  osmium  add  a 
few  crystals  of  thiourea  and  a  few  drops  of  hydrochloric 
acid,  and  warm.  Note  pink  to  red  color.  The  compound  is 
said  to  be  (Os(N2H4CS)6Cl3-H2O). 

Experiment  12.  Precipitation  of  elementary  osmium. 
(a)  To  a  solution  of  the  tetroxide  add  stannous  chloride. 

(6)  Try  the  action  of  zinc  and  hydrochloric  acid  upon 
a  solution  of  the  tetroxide. 

Experiment  13.  Odor  test  for  osmium.  Warm  a  dilute 
solution  of  osmium  tetroxide,  or  warm  with  nitric  acid  a 
solution  of  any  osmium  salt  of  the  lower  condition  of 
oxidation.  Note  the  odor. 

Experiment  14.  Precipitation  of  iridium  sulphide, 
(Ir2S3).  Pass  hydrogen  sulphide  through  a  solution  of 
iridium  tetrachloride.  Note  the  bleaching  of  color  pre- 
ceding precipitation.  Try  the  action  of  ammonium  sul- 
phide upon  the  precipitate. 

Experiment  15.  Formation  of  the  double  chlorides  of 
iridium  with  ammonium  and  potassium,  ((NH^IrCle  and 
K2IrCl6).  To  separate  portions  of  a  fairly  concentrated 
solution  of  iridium  tetrachloride  add  ammonium  chloride 
and  potassium  chloride  respectively. 

Experiment  16.     Action  of  sodium  hydroxide  upon  iridium 


1 82  THE  RARER  ELEMENTS. 

tetrachloride.  To  a  solution  of  indium  tetrachloride  add 
some  sodium  hydroxide  in  solution.  Note  the  changes  in 
color,  dark  red  to  green  (IrCls). 

2lrCU  +  2NaOH  =  2lrCl3+NaCl+H2O+NaOCl. 

Warm  the  solution  and  note  the  change  to  azure  blue. 

Experiment  17.  Reduction  of  iridium  salts,  (a)  To  a 
solution  of  iridium  tetrachloride  add  oxalic  acid. 

(b)  Try  similarly  the  action  of  zinc  upon  an  acid  solu- 
tion of  the  salt. 

Experiment  18.  Action  of  ammonium  hydroxide  upon  a 
rhodium  salt.  Add  ammonium  hydroxide  to  a  solution  of 
a  rhodium  salt  and  allow  to  stand. 

Experiment  19.  Precipitation  of  rhodium  sulphide, 
(Rh2S3).  Pass  hydrogen  sulphide  through  a  solution  of 
sodium-rhodium  chloride.  Try  the  action  of  ammonium 
sulphide  upon  the  sulphide  precipitated. 

Experiment  20.  Reduction  of  rhodium  salts.  To  an 
acid  solution  of  a  rhodium  salt  add  zinc. 

Experiment  2 1 .  Formation  of  the  double  nitrite  of  potas- 
sium and  rhodium,  (K3Rh(NO2)6).  To  a  solution  of  sodium- 
rhodium  chloride  add  potassium  nitrite  in  solution  and 
warm.  Try  the  action  of  hydrochloric  acid  upon  the 
precipitate. 

Experiment  22.  Precipitation  of  rhodium  hydroxide, 
(Rh(OH),).  Note  the  first  action  and  the  action  in  excess 
of  sodium  or  potassium  hydroxide  upon  a  solution  of  sodium- 
rhodium  chloride.  Boil  the  solution  just  obtained. 

Experiment  23.  Precipitation  of  ruthenium  sulphide, 
(Ru2S3).  (a)  To  a  solution  of  ruthenium  trichloride  add 
hydrogen  sulphide.  Note  the  blue  color  preceding  pre- 
cipitation. 

(b)  Use  ammonium  sulphide  as  the  precipitant. 

Experiment  24.  Formation  of  the  soluble  double  nitrite 
of  ruthenium  and  potassium,  (KaRuCNC^e)'  To  a  solution 


GOLD.  Ig3 

of  ruthenium  trichloride  add  a  solution  of  potassium  ni- 
trite. Note  the  color.  Add  ammonium  sulphide  to  the 
solution. 

Experiment  25.  Precipitation  of  ruthenium  hydroxide, 
(Ru(OH)s).  To  a  solution  of  ruthenium  trichloride  add 
sodium  or  potassium  hydroxide  in  solution. 

Experiment  26.  Precipitation  of  metallic  ruthenium. 
To  an  acid  solution  of  a  ruthenium  salt  add  metallic  zinc. 

GOLD,  Au,  197.2. 

Discovery.  Gold  is  probably  one  of  the  earliest  known 
of  the  metals.  In  very  ancient  records  frequent  mention 
is  made  of  its  uses.  As  far  back  as  3600  B.C.  in  the  Egyp- 
tian code  of  Menes  a  ratio  of  value  between  gold  and  silver 
(2.5:1)  is  mentioned.  Rock  carvings  of  Upper  Egypt 
dating  from  2500  B.C.  show  crude  representations  of  the 
washing  of  gold-bearing  sands  in  stone  basins,  and  of  the 
melting  of  the  metal  in  simple  furnaces  by  means  of  mouth 
blowpipes.  In  fact  the  discovery  of  gold  dates  back  to 
the  beginnings  of  civilization.  The  search  for  it  furnished 
the  motive  of  many  voyages  of  discovery  and  conquest, 
which  resulted  in  the  extension  of  civilization;  and  from 
the  desire  to  change  the  base  metals  into  gold  sprang  the 
study  of  alchemy,  from  which  developed  the  science  of 
chemistry. 

Occurrence.  Gold  occurs  in  nature  both  free  and  in 
combination.  Free  or  native  gold  is  found  (i)  as  vein 
gold,  in  the  quartz  veins  which  intersect  metamorphic 
rocks,  and  (2)  as  placer  gold,  generally  in  the  form  of  grains 
or  nuggets,  in  alluvial  deposits  of  streams.  Native  gold  is 
usually  alloyed  with  silver,  which  sometimes  amounts  to  as 
much  as  fifteen  per  cent,  of  the  alloy.  Iron  and  copper 
are  sometimes  present,  and  bismuth,  palladium,  and  rho- 
dium alloys  are  known. 


184  THE  RARER  ELEMENTS. 

In  combination  gold  is  found  as  follows: 

Petzite,  (AgAu)2Te,                      contains 18-24%  Au 

Sylvanite,   AuAg)Te2,  "  26-29%   " 

Goldschmidtite,  Au2AgTe6,  "  31-32%   " 

Krennerite,  (Au,Ag)Te2-AuTe2,        "  30-34%   " 

Calaverite,  (Au,Ag  Te2-AuTe2,  "  38-42%   " 

Kalgoorlite,  HgAu2Ag6Te6,  "  20-21%   " 

Nagyagite,  Au2Pb14Sb3Te7S17,  5-"%    " 

Muthmannite,  (Au,Ag)Te  22-23%   " 

Extraction.  The  six  processes  indicated  below  follow 
the  principal  methods  that  have  been  employed  for  the 
extraction  of  gold. 

(1)  Washing  or  Hydraulicking.     This  method  is  applied 
mainly    to    placer    deposits.     Powerful   jets    of  water  are 
directed   upon  the  gold-bearing   sands,    causing   them   to 
pass  through  a  series  of  sluices.     Because  of  its  higher 
specific  gravity  the  gold  is  largely  left  behind,  while  the 
other  materials  are  carried  away. 

(2)  Amalgamation    (primitive}.     In     this     process    the 
crushed  ore  or  the  gold-bearing  sand  is  first  washed,  to 
remove  the  greater  part  of  the  light,  worthless  material, 
and  the  remainder  is  rubbed  with  mercury  in  a  mortar. 
The   amalgam   thus   obtained   is   heated,    where'upon   the 
mercury  is  volatilized  and  the  gold  remains. 

(3)  Stamp  battery  amalgamation.     The  ore  is  pulverized 
and  mixed  with  water,  and  in  the  form  of  pulp  caused  to 
pass  over  a  series  of  amalgamated  copper  plates.     Gold 
amalgam  forms  on  the  plates,  and  from  time  to  time  it  is 
removed  and  cupelled. 

(4)  Chlorination.     (a)  Vat    process.     The   crushed   ore 
is  placed  loosely  in  large  vats  and  moistened  with  water. 
Chlorine  is  forced  in,  and  the  whole  is  allowed  to  stand  for 
about  twenty-four  hours.     The  mater'al  is  then  leached 
with  water  until  the  washings  give  no  further  test  for  gold. 
The  solution  of  gold  chloride  thus  obtained  is  treated  with 


COLD.  !85 

sulphur  dioxide,  to  destroy  the  excess  of  chlorine,  and  then 
with  hydrogen  sulphide.  The  gold  sulphide  thus  precipi- 
tated is  decomposed  with  borax  and  the  gold  is  melted 
into  bullion. 

(6)  Barrel  process.  Into  large  barrels  are  put  water 
and  sulphuric  acid,  the  ore,  and  chloride  of  lime.  The 
barrels  are  then  closed  and  rotated  for  a  period  varying  from 
one  hour  to  four  hours.  At  the  end  of  that  time  the  con- 
tents are  leached  and  the  gold  is  extracted  as  described 
above. 

The  chlorination  process  is  generally  applied  to  low- 
grade  ores,  and  these  must  have  been  roasted  unless  the 
gold  occurs  in  them  native. 

(5)  Cyanide  process.     The  ore,   ground  fine,  is  placed 
in  large  vats,  and  a  dilute  solution  (.2-.  5%)  of  potassium 
cyanide  is  forced  in.    After  a  time  the  solution  is  drawn  off 
and  passed  over  zinc  shavings,  upon  which  the  gold  is  de- 
posited as  a  black  slime.     The  mixture  of  zinc  and  gold 
is  either  treated  with  sulphuric  acid,  to  dissolve  the  zinc,  or 
roasted  with  a  flux  of  niter  and  carbonate  of  soda.     The 
reactions  which  take  place  in  the  cyanide  process  may  be 
represented  as  follows : 

(1)  4Au  +  8KCN  +  02  +  2H20  =  4KAu(CN)2  +  4KOH. 

(2)  2KAu(CN)2  +  2Zn  +  2H2O  = 

2KOH  +  H2  +  2Zn(CX),  +  2Au. 

(6)  Smelting.     In  smelting  the  gold  ore  is  mixed  with 
some  other    metallic    ore    appropriately  chosen,   and  the 
mixture   is   subjected   to   intense   heat.     The   gold   alloys 
with  the  other  metal,  and  the  alloy  is  separated  from  the 
residue,  or  slag,  and  worked  for  gold.     Three  modifications 
of  this  important  process  are  in  common  use,  viz.,  lead, 
copper  matte,   and  iron  matte  smelting.     The  process  of 
lead-smelting  is  in  outline  as  follows:    The  alloy  obtained 
by  heating  a  mixture  of  gold  and  lead  ores  is  melted  with 
.zinc.    The  gold  and  silver  combine  with  the  zinc  and  rise 


186  THE  RARER    ELEMENTS. 

to  the  surface,  leaving  the  lead  below.  The  alloy  of  gold, 
silver,  and  zinc  is  then  skimmed  off  and  roasted.  The  zinc 
passes  off,  leaving  the  gold  and  silver,  which  are  separated 
by  electrolysis. 

The  Element.  A.  Preparation.  As  extracted  from  its 
ores  gold  is  in  the  elementary  condition  (vid.  Extraction). 

B.  Properties.  Of  a  characteristic  yellow  color,  gold 
is  the  most  malleable  and  ductile  of  the  metals.  It  is  about 
as  soft  as  silver.  It  is  insoluble  in  the  common  acids,  but 
is  attacked  by  aqua  regia,  chlorine,  bromine,  and  by  potas- 
sium cyanide  in  the  presence  of  oxygen.  It  is  dissolved 
in  many  reactions  where  oxygen  is  set  free,  e.g.  by  selenic 
acid,  and  by  phosphoric  or  sulphuric  acid  in  the  presence 
of  telluric  acid,  nitric  acid,  lead  or  manganese  dioxide, 
chromium  trioxide,  or  potassium  permanganate.  It  is 
not  attacked  when  suspended  in  sulphuric  acid  and  treated 
with  oxygen  gas  (Lenher,  Jour.  Amer.  Chem.  Soc.  xxvi, 
550).  It  is  somewhat  soluble  in  hydrochloric  acid  in  the 
presence  of  light  and  manganous  chloride  (Berthelot, 
Compt.  rend,  cxxxvm,  1297),  and  in  thiocarbamide  in 
the  presence  of  oxidizing  agents  (Moir,  Proc.  Chem.  Soc. 
xxn,  105,  165).  It  has  also  been  found  to  be  slightly 
attacked  by  alkali  sulphides  and  thiosulphates.  Moissan 
has  distilled  it  in  the  electric  furnace;  he  finds  that  when 
alloys  of  copper  or  tin  with  gold  are  subjected  to  distilla- 
lion,  the  copper  and  tin  distil  first  (Compt.  rend.  CXLI, 
853,977).  Its  melting-point  is  1037°  C.,* — just  above  that 
of  copper.  Gold  alloys  with  nearly  all  the  metals.  It  is 
occasionally  found  crystallized  in  the  cubic  system.  It  is 
a  good  conductor  of  heat  and  electricity.  Its  specific 
gravity  is  19.49. 

Compounds.f  A.  Typical  forms.  The  following  com- 
pounds of  gold  may  be  considered  typical  forms : 

*  U.  S.  Bureau  of  Standards  gives  1063°  C. 

t  For  a  discussion  of  some  complex  compounds  see  Gutbier,  Ztschr.  anorg. 
Chem.  LXXXV,  353. 


COLD. 
Au,0, 

Au,Cl4 
Au,Br4 


187 


Oxides Au,O 

Hydroxide 

Aurates 

Chlorides AuCl 

Double     chlorides, 
many  of  the  types 


Bromides AuBr 

Double     bromides, 

of  the  type 

Iodides Aul 

Double  iodides,  of 

the  type 

'Sulphides Au,S 

Double  sulphides. .  Au?S-Na?S 


Sulphites  (double)  Au,SCy  3NajSOj+ 3H2O 

S-lphates AuSO, 

Nitrate 

Cyanides AuCN 

Double  cyanides.  .  AuCN-KCN 
Sulphocyanides.  .  .AuCNS-KCNS 


Au,0, 
Au(OH), 
Na2O2-  Au2O,  * 
BaO2-Au2O,,  etc. 
AuCl, 

AuCl3-RCl 

AuClj-RCl, 
AuBrs 

AuBr3-RBr 
AuI3 

AuI3-RI 


Au2(  SO3)  3  •  5  K,SO3+  5  H2O 


Au(N03)3-HNOj 

Au(CN), 

Au(CN)3.KCN,etc. 

Au(CNS),-KCNS 


B.  Characteristics.  The  compounds  of  gold  are  known 
chiefly  in  two  conditions  of  oxidation,  of  which  aurous 
oxide,  (Au2O),  and  auric  oxide,  (Au2O3),  serve  as  types. 
When  metallic  gold  is  dissolved  in  aqua  regia  auric 
chloride  is  formed,  a  yellow  crystalline  salt  soluble  in 
water;  when  auric  chloride  is  heated  to  180°  C.  it  goes 
over  to  aurous  chloride,  a  white  powder  insoluble  in 
water.  The  aurous  salts  resemble  the  salts  of  silver 
and  of  copper  in  the  cuprous  condition;  the  auric  salts 
resemble  those  of  aluminum  and  of  iron  in  the  ferric 
condition.  The  auric  hydroxide,  (Au(OH)3),  is  acidic 
in  character  and  unites  with  bases  to  form  aurates  of  the 

type   RAuO2.     Hydrogen  sulphide  precipitates  brownish- 
black  auric  sulphide,  (Au2S3  or  Au2S2+S),  from  cold  solu- 


*  See  Meyer,  Compt.  rend.  CXLV,  805. 


1 88  THE  RARER  ELEMENTS. 

tions  of  gold  salts,  and  steel-gray  aurous  sulphide,  (Au2S  or 
Aii2S+S),  from  hot  solutions.  Salts  of  gold  in  solution 
are  easily  reduced  to  the  metal  by  reducing  agents. 

Estimation.*  A.  Gravimetric.  Gold  is  weighed  as  the 
metal.  From  solutions  it  is  precipitated  by  reducing  agents, 
such  as  ferrous  sulphate,  oxalic  acid,  formaldehyde,  and 
hydrogen  dioxide  in  alkaline  solution  (see  also  Lenher,  Jour. 
Amer.  Chem.  Soc.  xxxv,  546;  xxxvi,  1423). 

B.  Volumetric.  Gold  may  be  determined  volumetrically 
(i)  by  allowing  potassium  iodide  to  act  upon  auric  chloride, 
(AuCl3+3KI=3KCl+Ai;I+I2),  and  estimating  the  iodine 
thus  freed  by  means  of  thiosulphate  (Peterson,  Zeitsch. 
anorg.  Chem.  xix,  63 ;  Gooch  and  Morley,  Amer.  Jour. 
Sci.  [4]  vin,  261;  Maxson,  Amer.  Jour.  Sci.  [4]  xvi,  155; 
Lehher,  Jour.  Amer.  Chem.  Soc.  xxxv,  733);  (2)  by 
warming  a  solution  of  auric  chloride  with  a  measured 
amount  of  arsenious  acid  solution  which  must  be  in  ex- 
cess, (3As2O3+4AuCl3+6H2O  =  3As2O5  +  i2HCl+4Au),  and 
determining  the  excess  of  arsenious  acid  by  iodine  in 
the  usual  way  (Rupp,  Ber.  Dtsch.  chem.  Ges.  xxxv,  2011; 
Maxson,  loc.  cit.}. 

Separation.  Gold  and  platinum  fall  into  the  analyt- 
ical group  of  arsenic,  antimony,  and  tin.  From  these 
they  may  be  separated  by  the  following  process:  fusion 
of  the  sulphides  with  sodium  carbonate  and  niter,  and 
removal  of  the  arsenic  by  extraction  with  water ;  treatment 
of  the  insoluble  residue  with  zinc  and  hydrochloric  acid, 
which  reduces  the  tin  and  antimony  to  the  metallic  con- 
dition; boiling  with  hydrochloric  acid,  which  dissolves  the 
tin;  then  with  nitric  and  tartaric  acids,  which  dissolves 
the  antimony,  leaving  gold  and  platinum. 

For  the  separation  of  gold  from  platinum  and  the  plat- 
inum metals  vid.  Platinum. 

*  See  Hillebrand,  Bull.  253  (1905),  U.  S.  Geological  Survey;  Bahney,  Bull. 
Am.  Inst.  Mining  Eng.  (1915),  339;  Christensen,  Ztschr.  anal.  Chem.  LIV,  158; 
Smoot,  Enrr.  Mining  J.  xcix,  700. 


EXPERIMENTAL   WORK  ON  COLD.  189 

From  selenium  and  tellurium  gold  may  be  separated 
by  oxalic  acid,  which  precipitates  the  gold  (A.  A.  Noyes 
Jour.  Amer.  Chem.  Soc.  xxix,  137). 


EXPERIMENTAL  WORK  ON  GOLD. 

Experiment  i.  Extraction  of  gold  from  its  ores.  (a) 
Digest  for  several  hours  in  a  beaker  on  a  steam-bath  about 
100  grm.  of  finely  ground  gold  ore  with  a  dilute  solution  of 
potassium  cyanide,  adding  water  from  time  to  time  to  re- 
place the  liquid  evaporated.  Filter,  pass  the  filtrate  several 
times  through  a  funnel  containing  zinc  shavings,  until  upon 
testing  the  liquid  with  a  fresh  piece  of  zinc  no  discoloration 
of  the  metal  is  observed.  Dissolve  the  zinc  in  hydrochloric 
acid  to  remove  the  black  deposit.  Filter,  dissolve  the  resi- 
due in  aqua  regia,  remove  the  excess  of  acid  by  evaporation, 
and  test  for  gold  by  stannous  chloride,  ferrous  sulphate,  etc. 

(6)  Mix  in  a  glass-stoppered  bottle  about  100  grm.  of 
finely  ground  ' '  oxidized ' '  or  previously  roasted  ore  with  a 
little  bleaching  salt  and  enough  water  to  give  the  mass  the 
consistency  of  thin  paste.  Then  add  gradually  enough 
sulphuric  acid  to  start  an  evolution  of  chlorine.  Close  the 
bottle  and  shake  it,  to  insure  a  thorough  mixing  of  the 
contents.  Allow  the  action  to  go  on  for  several  hours, 
agitating  the  mass  occasionally,  and  taking  care  to  have  an 
excess  of  chlorine  present  throughout  the  process.  Extract 
with  water,  concentrate  if  necessary,  and  test  for  go'd  in 
the  solution.  A  two  per  cent,  solution  of  bromine  may  be 
substituted  for  the  materials  generating  chlorine. 

Experiment  2.  Precipitation  of  the  sulphide  of  gold, 
(Au2S3  or  Au2S2  +  S  ?) .  Into  a  cold  solution  of  auric  chloride 
pass  hydrogen  sulphide.  Try  the  action  of  yellow  am- 
monium sulphide  upon  the  precipitate. 

Experiment  3.  Formation  of  aurous  iodide,  (Aul).  To 
a  solution  of  auric  chloride  add  a  few  drops  of  a  dilute 


IQO  THE  RARER  ELEMENTS. 

solution  of  potassium  iodide.  Note  the  precipitate,  and 
the  solvent  action  of  an  excess  of  the  reagent. 

Experiment  4.  Formation  of  gold  iminochloride  and  gold 
iminoamide,  "fulminating  go/d,"(Au(NH)Cl+Au(NH)NH2). 
To  a  very  dilute  solution  of  gold  chloride  add  a  little 
ammonium  hydroxide. 

CAUTION.  Do  not  attempt  to  isolate  the  precipitate. 
Note  that  neither  potassium  nor  sodium  hydroxide  gives 
a  precipitate  under  similar  conditions  of  dilution,  because 
gold  hydroxide  is  very  soluble  in  excess. 

Experiment  5.  Formation  of  the  "  purple  of  Cassius."* 
To  a  very  dilute  solution  of  a  gold  salt  add  a  drop  or  two 
of  dilute  stannous  chloride  solution. 

Experiment  6.  Precipitation  of  gold.  To  separate  por- 
tions of  a  slightly  acidified  solution  of  a  gold  salt  add  solu- 
tions of  ferrous  sulphate,  oxalic  acid,  and  hydrazine  sulphate 
or  chloride.  Try  also  the  action  of  hydrogen  dioxide  upon 
an  alkaline  solution  of  a  gold  salt.  Note  the  color  of  the 
precipitated  gold  by  transmitted  and  reflected  light. 

Experiment  7.  Solvent  action  of  certain  reagents  upon 
gold.  Try  separately  upon  metallic  gold  the  action  of 
aqua  regia,  chlorine  or  bromine  water,  and  a  dilute  solution 
of  potassium  cyanide. 

*  Grunwald  (Sprechsaal  XLIH,  410)  gives,  as  the  composition  of  the  "  purple 
of  Cassius,"  hydrogel  of  stannic  acid  colored  by  colloidal  gold;  vid.  also  Zsigmondy, 
Ann.  Chem.  Pharm.  ccci,  361. 


CHAPTER  XI. 
THE  RARE   GASES  OF  THE  ATMOSPHERE. 

Argon,  A,  39.88  Krypton,  Kr,  82.92 

Helium,  He,  4.  Neon,  Ne,  20.2 

Xenon,  X,  130.2 

Discovery.  In  1892  Lord  Rayleigh,  while  engaged  in 
the  study  of  the  density  of  elementary  gases,  made  the  im- 
portant observation  that  the  nitrogen  obtained  from  nitric 
acid  or  ammonia  was  about  one  half  of  one  per  cent,  lighter 
than  atmospheric  nitrogen  (Proc.  Royal  Soc.  LV,  340). 
An  investigation  of  this  difference  led  to  the  discovery 
two  years  later  of  the  gas  Argon  (apyos,  inert)  by  Lord 
Rayleigh  and  Professor  William  Ramsay  (Proc.  Royal 
Soc.  LVII,  265;  Amer.  Chem.  Jour,  xvn,  225).  An  experi- 
ment made  by  Cavendish  in  1785  seems  also  to  have  resulted 
in  the  separation  of  this  gas  (Phil.  Trans.  Roy.  Soc.  (1785) 
LXXV,  372,  and  (1788)  LXXVIII,  271). 

In  the  course  of  analytical  work  on  uraninite  undertaken 
by  Hillebrand  in  1888,  a  gas  which  he  thought  to  be  nitro- 
gen was  obtained  upon  the  boiling  of  the  mineral  with  dilute 
sulphuric  acid  (Bull.  U.  S.  Geol.  Sur.  No.  78,  p.  43 ;  Amer. 
Jour.  Sci.  [3]  XL,  384).  In  1895  Ramsay,  whose  attention 
had  been  called  to  Hillebrand 's  work,  and  who  doubted 
whether  nitrogen  could  be  obtained  by  the  method  de- 

191 


IQ2  THE  RARER  ELEMENTS. 

scribed,  prepared  some  of  the  gas  by  Hillebrand's  process 
from  cleveite,  a  variety  of  uraninite.  He  then  sparked  the 
gas  with  oxygen  over  soda  to  remove  the  nitrogen.  Ob- 
serving very  little  contraction,  he  removed  the  excess  of 
oxygen  by  absorption  with  potassium  pyrogallate  and 
examined  the  residual  gas  spectroscopically.  The  spec- 
trum showed  argon  and  hydrogen  lines,  and  in  addition  a 
brilliant  yellow  line,  (D3),  coincident  with  the  helium  line 
of  the  solar  chromosphere  discovered  by  Lockyer  in  1868 
(Proc.  Royal  Soc.  LVIII,  65,  81).  The  only  previous  note 
regarding  helium  as  a  terrestrial  element  is  a  statement 
by  Palmieri,  in  1881,  that  a  substance  ejected  from  Vesu- 
vius showed  the  line  D3  (Rend.  Ace.  di  Napoli  xx,  233); 
he  failed  to  describe  his  treatment  of  the  material,  how- 
ever, and  he  seems  to  have  made  no  further  investigation  of 
the  subject.  Kayser  first  detected  helium  in  the  atmos- 
phere, in  1895  (Chem.  News  LXXII,  89),  several  months 
after  Ramsay's  discovery. 

The  year  1898  witnessed  the  discovery  by  Ramsay  and 
Travers  of  three  other  inert  atmospheric  gases.  Having 
allowed  all  but  one  seventy-fifth  of  a  given  amount  of 
liquid  air  to  evaporate,  and  having  removed  the  oxygen 
and  nitrogen  remaining  by  sparking  over  soda,  they  ob- 
tained a  small  amount  of  a  gac  which,  while  showing  a  feeble 
spectrum  of  argon,  gave  new  lines  as  well.  This  newly 
discovered  gas  they  named  Krypton,  from  KPVTTTOS,  hid- 
den (Proc.  Royal  Soc.  LXIII,  405). 

By  fractioning  the  residue  after  the  evaporation  of  a 
large  amount  of  liquid  air  they  found  evidence  of  a  gas  of 
greater  density  than  krypton,  and  for  this  heavy  gaseous 
element  the  name  Xenon  (gevos,  stranger)  was  chosen 
(Chem.  News  LXXVIII,  154). 

The  third  discovery  of  the  year  by  the  same  investigators 
was  that  of  Neon  (reos,  new),  a  gas  of  less  density  than 
argon.  The  first  fraction  obtained  from  the  evaporation 


THE  RARE  CASES  OF   THE  ATMOSPHERE.  193 

of  liquid  air  was  mixed  with  oxygen  and  sparked  over 
soda,  and  the  excess  of  oxygen  was  removed  by  phosphorus. 
The  remaining  gas  yielded  a  new  and  characteristic  spectrum 
(Proc.  Royal  Soc.  LXIII,  437). 

Occurrence.*  Argon  forms  about  one  per  cent,  of  the 
air  by  volume.  It  is  found  in  small  quantities  in  gases 
from  certain  mineral  springs,  e.g.  Bath,  Cauterets,  Wild- 
bad,  Voslau,  the  sulphur  spring  of  Harrogate;  in  the  gases 
occluded  in  rock  salt,  and  in  some  volcanic  gases  (Moissan, 
Compt.  rend,  cxxxvm,  936;  cxxxv,  1085).  It  has  been 
detected  in  some  helium-bearing  minerals,  e.g.  cleveite, 
broggerite,  uraninite,  and  malacon. 

Helium,  the  existence  of  which  was  first  observed  in 
the  sun,  occurs  in  very  small  proportion  in  the  terrestrial 
atmosphere.  The  chief  sources  of  the  gas  have  been  certain 
rare  minerals,  among  which  are  uraninite  (pitch-blende), 
cleveite,  monazite,  fergusonite,  samarskite,  columbite,  and 
malacon.  It  has  been  found  also  in  some  mineral  springs, 
e.g.  Bath,  Cauterets,  Adano,  and  Wildbad,  and  in  natural 
and  "wind"  gases  in  amounts  varying  from  traces  to  2%. 
The  gases  yielding  the  largest  percentages  are  those  of 
southern  Kansas  and  northern  Oklahoma. 

The  other  gases  of  this  group  are  present  in  the  air  in 
very  minute  quantities.  Neon  is  said  to  constitute  0.002  5% 
and  krypton  0.00002%  of  the  atmosphere.  Traces  of  neon 
have  been  detected  in  the  helium  from  the  springs  of  Bath, 

Extraction.  Argon,  contaminated  with  a  greater  or  less 
percentage  of  the  associated  gases,  may  be  extracted  by  the 
following  methods:  • 

*  See  also  Ramsay,  Chem.  News  LXXXVH,  159;  Nasini,  Chem.  Zentr.  (1004) 
n,  77;  Pesendorfer,  Chem.  Ztg.  xxix,  359;  Rutherford,  Chem.  Zentr.  (1905) 
i,  848;  Kohlschiitler,  Ber.  Dtsch.  chem.  Ges.  xxxvin,  1419;  Prytz,  Chem.  Zentr, 
(1905)  n,  1570;  Ewers,  Chem.  Zentr.  (1906)  i,  1319;  Moureu,  Compt.  rend. 
CXLII,  1155;  CXLIII,  795;  Kitchin,  Jour.  Chem.  Soc.  LXXXIX,  1568;  Czako,  Ztschr. 
anorg.  Chem.  LXXXII,  249;  Chem.  News  cvm,  16;  Collie,  Jour.  Chem.  Soc.  cm, 
419;  Piutti,  Atti  R.  Accad.  dei  Lincei,  Roma  [5]  xxn,  I,  140;  Sieveking,  Chem. 
Zentr.  (1913)  I,  52. 


194  THE   RARER    ELEMENTS. 

(1)  From  atmospheric  nitrogen.* — The  nitrogen  is  passed 
over  red-hot  magnesium  filings;   a  nitride  is  thus  formed, 
while  the   argon   is  left  uncombined  (Ramsay).     Heated 
lithium  may  be  substituted  for  magnesium. 

(2)  From  air.     Induction  sparks  are  passed  through  a 
mixture  of  oxygen  and  air  contained  in  a  vessel  which  is 
inverted  over  caustic  -potash.     The  oxygen  and  nitrogen 
combine  and  dissolve  in  the  potassium  hydroxide,  leaving 
the  argon  (Rayleigh). 

Helium  may  be  obtained  from  its  mineral  sources  by 
boiling  the  material  with  dilute  sulphuric  acid,  or  by  heat- 
ing in  vacua .  From  its  gaseous  sources  it  is  obtained  f  by 
subjecting  the  gaseous  mixtures  to  very  low  temperatures 
which  cause  the  other  gases  except  helium  to  liquefy. 

Krypton  and  xenon  are  extracted  as  follows:  After 
the  evaporation  of  a  large  amount  of  liquid  air  the  residue 
is  freed  from  oxygen  and  nitrogen  and  liquefied  by  the 
immersion  of  the  containing  vessel  in  liquid  air.  The 
greater  part  of  the  argon  can  be  removed  as  soon  as  the 
temperature  rises.  By  repetitions  of  this  process  the 
three  gases  can  be  separated  from  one  another,  krypton 
exercising  much  greater  vapor  pressure  than  xenon  at  the 
temperature  of  boiling  air  (Ramsay  and  Travers,  Proc. 
Royal  Soc.  LXVII,  330). 

Neon  is  obtained  from  the  gas,  largely  nitrogen,  that 
first  evaporates  from  liquid  air.  This  gas  is  liquefied,  and 
a  current  of  air  is  blown  through  it.  The  material  that 
first  evaporates  is  passed  over  red-hot  copper,  to  remove 
the  oxygen,  and  after  being  freed  from  nitrogen  in  the 
usual  manner,  is  liquefied.  By  fractional  distillation  helium 
and  neon  are  removed,  and  argon  is  left  behind.  By  the 
use  of  liquefied  hydrogen  helium  and  neon  are  separated, 
as  neon  is  liquefied  or  solidified  at  the  temperature  of  boil- 

*  Hamburger  determines  the  composition  of  argon-nitrogen  mixtures  by  ob- 
serving the  different  condensation  rates  in  liquid  air  (Zts^hr.  angew.  Chem. 
xxvin,  I,  75). 

f  Rogers,  Nat.  Geog.  Mag.  xxxv,  441. 


THE  RARE    CASES    OF   THE  ATMOSPHERE.  195 

ing  hydrogen,  while  helium  remains  gaseous.  Several  frac- 
tionations  are  necessary  to  obtain  pure  neon  (Ramsay  and 
Travers,  Proc.  Royal  Soc.  LXVII,  330). 

Properties.  The  newly  discovered  constituents  of  the 
atmosphere  are  inert,  colorless,  probably  monatomic  gases; 
which  have  not  been  known  to  form  definite  compounds.* 

Argon  is  somewhat  soluble  f  in  water.  Its  density  is, 
19.96  and  its  specific  heat  1.645.  It  solidifies  at  -191°  C., 
melts  at  -189.5°  C.,  and  boils  at  -185°  C.  It  has  been 
condensed  to  a  colorless  liquid  (Baly  and  Donnan,  Jour, 
Chem.  Soc.  (London)  LXXXI,  914).  Argon  gives  two  dis- 
tinct spectra,  according  to  the  strength  of  the  induction 
current  employed  and  the  degree  of  exhaustion  in  the  tube. 
When  the  pressure  of  the  argon  is  3  mm.  the  discharge  is 
orange-red  and  the  spectrum  shows  two  particularly  prom- 
inent red  lines.  J  If  the  pressure  is  further  reduced,  and  a 
Leyden  jar  is  intercalated  in  the  circuit,  the  discharge 
becomes  steel-blue  and  the  spectrum  shows  a  different 
set  of  lines  (Crookes,  Amer.  Chem.  Jour,  xvn,  251). 

Helium  is  slightly  soluble' §  in  water.  Its  density 
is  1.98,  and  it  boils  at  about  -268.5°  C.  It  was  liquefied 
by  Onnes  (Proc.  k.  Akad.  Wetensch.  Amsterdam  xi,  168; 
xin,  1093)  and  its  density  in  liquid  form  was  found  to  be 
0.122.  Its  spectrum  1 1  is  characterized  by  five  brilliant 
lines, — one  each  in  the  red,  yellow,  blue-green,  blue,  and 
violet.  Reference  has  already  been  made  to  the  yellow 
line  D3. 

Krypton  is  less  volatile  than  argon.  Its  density  is 
41.5.  Its  melting-point  is  given  as  -169°  C.,  and  its  boiling- 
point  as  -152°  C.I  Its  spectrum**  is  characterized  by  a 
bright  line  in  the  yellow  and  one  in  the  green. 

*  Fisher  and  Schroter,  Ber.  Dtsch.  chem.  Ges.  XLHI,  1435,  1442,  1454,  1465. 

t  100  volumes  of  water  will  dissolve  3.7  volumes  of  argon  at  20°  C. 

J  Paulson,  Physik  xv,  831. 

§  100  volumes  of  water  will  dissolve  about  1.4  volumes  of  helium  at  20°  C. 

||  Curtis,  Proc.  Royal  Soc.  LXXXIX,  146. 

If  Erdmann,  Chem.  Ztg.  xxxi,  1075. 

**  See  Baly,  Proc.  Royal  Soc.  LXXII,  84.  — -. 


196  THE    RARER   ELEMENTS. 

Xenon  also  is  less  volatile  than  argon,  and  it  has  a 
much  higher  boiling-point.  Its  density  is  65.35.  Its 
melting-point  is  said  to  be  -140°  C.,  and  its  boiling-point 
-109°  C.*  Its  spectrum  f  is  similar  in  character  to  that 
of  argon,  though  the  position  of  the  lines  is  different. 
With  the  ordinary  discharge  the  glow  in  the  tube  is  blue 
and  the  spectrum  shows  three  red  and  about  five  brilliant 
blue  lines.  With  the  jar  and  spark-gap  the  glow  changes 
to  green  and  the  spectrum  is  characterized  by  four  green 
lines  (Ramsay  and  Travers,  Chem.  News  LXXVIII,  155). 

Neon  is  more  volatile  than  argon.  Its  density  is  10.1. 
Its  melting-point  is  given  as  -253°  C.,  and  its  boiling- 
point  as  -243°  C4  Its  spectrum  §  is  characterized  by 
bright  lines  in  the  red,  orange,  and  yellow,  and  faint  lines 
in  the  blue  and  violet. 

*  Erdmann,  Chem.  Ztg.  xxxi,  1075. 

t  See  Baly,  Proc.  Royal  Soc.  LXXII,  84. 

|  Erdmann,  loc.  cit.;  Dewar,  Proc.  Royal  Soc.  Lxvin,  360. 

§  See  Baly,  loc.  cit.;  Merton,  ibid.  LXXXIX,  447. 


CHAPTER    XII. 

SOME  TECHNICAL  APPLICATIONS  OF  THE  RARER 
ELEMENTS.* 

Lithium  has  found  some  use  in  the  preparation  of  artificial 
mineral  waters  and  in  medicine.  It  has  also  been  used 
in  fireworks  and  signal  rockets  (U.  S.  Press  Bull.  May,  1918). 

Beryllium  compounds  are  said  to  have  been  employed 
in  the  manufacture  of  mantles  for  incandescent  gas  lighting 
(Baskerville,  Eng.  and  Min.  Jour.  LXXXVI,  907). 

The  use  of  radium  in  medicine  is  well  known.  Its  em- 
ployment in  the  manufacture  of  luminous  paints  has  devel- 
oped greatly  during  the  war.  Mesothorium  is  also  being 
used  in  luminous  paints.  (Met.  Chem.  Eng.  xvn,  357 ;  Eng. 
and  Min.  Jour.  (1918)  1124). 

The  chlorides  of  the  rare  earthsf  have  been  subjected  to 
electrolysis  (Muthmann  and  Weiss,  Liebig,  Ann.  cccxxxi,  i ; 
cccxxxvn,  370),  and  have  yielded  a  so-called  "mischmetal" 
(45%  Ce,  35%  La,  Pr,  Nd,  and  20%  Sm,  Er,  Gd,  Y),  with 
which,  as  with  aluminum  in  the  Goldschmidt  process,  it 
has  been  found  possible  to  reduce  a  number  of  the  oxides 
(e.g.  Mo03,  V205,  Nb2O5,  and  Ta2O5)  to  the  elementary 
condition.  The  oxides  of  cerium,  neodymium,  praseo- 
dymium, and  erbium  seem  to  promise  some  application  in 
the  coloring  of  porcelain  and  glass  (Waegner,  Chem.  Ind. 
(1904)  xxvii,  No.  12).  Cerium  salts  have  been  used,  like 
aluminum  salts,  as  mordants  in  dyeing  (Witt,  Chem.  Ind. 

*  In  Mineral  Foote-Notes  published  bi-monthly  by  the  Foote  Mineral  Co.  of 
Philadelphia,  Penn.,  the  author  of  this  book  has  reviews  of  the  most  recent  technical 
literature  upon  the  rarer  elements. 

t  A  good  summary  of  the  technological  uses  of  the  rare  earths  thorium  and 
zirconium  may  be  found  in  Levy,  The  Rare  Earths,  Chapter  XXI  (Longmans, 
Green  and  Company),  and  Johnstone,  The  Rare  Earth  Industry  (Lock wood, 
London). 

197 


I98  THE  RARER    ELEMENTS. 

xix,  156),  and  Barbieri  (Atti  R.  Accad.  Lincei,  Roma  [5] 
xvi  [i],  395)  has  described  their  uses  as  catalyzing  agents, 
their  behavior  being  similar  to  that  of  manganese  com- 
pounds. Ceric  sulphate  has  been  used  in  photography  to 
reduce  the  density  of  negatives  (Lumiere  freres  and  Sey- 
wetz,  Chem.  Ztg.  Repert.  (1900),  80),  and  both  eerie 
nitrate  and  eerie  sulphate  have  been  used  in  making  photo- 
graphic paper  (Lumiere,  Compt.  rend.  (1893)  cxvi,  574; 
Chem.  Ztg.  Repert.  (1892),  180,  235).  Cerium  oxalate, 
cerium  hypophosphate,  and  cerium-ammonium  citrate  have 
found  uses  in  medicine  for  sea-sickness  and  nervous  dis- 
orders. The  nitrates  and  salicylates  of  the  rare-earth 
elements  are  used  as  antiseptic  agents  (Merck's  Ber.  (1897), 
39;  Kopp,  Therap.  Monatshefte  (1901),  Feb.  No.  2).  For 
purposes  of  oxidation  eerie  sulphate  has  been  found  to  be 
a  fair  substitute  for  well-known  oxidizing  agents  such  as 
potassium  permanganate  (Zeitsch.  f.  Electrochem.  ix,  534; 
Chem.  Ztg.  xxix,  669).  Salts  of  yttrium,  lanthanum, 
erbium,  and  ytterbium  have  been  used  in  disinfecting  and 
in  embalming.  Praseodymium  hydroxide  and  the  acetates 
of  praseodymium,  neodymium,  and  lanthanum  have  been 
employed  as  mordants,  as  have  also  mixtures  of  the  sul- 
phates of  these  earths  (Baskerville  and  Foust).  The  use 
of  the  peroxides  of  the  cerium  earths  in  making  rust-proof 
colors  has  been  suggested.  Cerium  compounds  are  finding 
extensive  use  in  the  manufacture  of  arc-lamp  electrodes 
(English  Patents  414,707  (1910);  21,374  and  8,150  (1909)). 
Oxygen  compounds  of  the  rare  earths  have  been  employed 
as  catalytic  agents  in  the  sulphuric  acid  contact  process, 
and  some  of  the  chlorides  have  been  used  as  contact  mate- 
rial in  decomposing  heated  hydrochloric  acid  gas.  Cerous- 
ceric  sulphate  has  found  use  in  the  manufacture  of  electric 
batteries  (Baskerville,  Paper  on  the  Uses  ,of 'the  Rare  Earths). 
The  employment  of  cerium  alloys,  pyrophoric  bodies,*  in 

*  Kellerman,  Die  Ceritmetalle  und  ihre  pyrophoren  Legierungen,  pub.  by 
W.  Knapp,  Halle  (1912). 


SOME  TECHNICAL   APPLICATIONS.  199 

gas  and  cigar  lighters  is  fairly  familiar  (Bohm,  Chem.  Ztg. 
xxxiv,  361;  Dederichs,  Pharm.  Post,  XLVI,  397). 

The  use  of  thorium  nitrate  in  the  manufacture  of  mantles 
for  incandescent  gas  lights  is  a  well-known  application  of  tho- 
rium, and  the  development  of  this  growing  and  important  in- 
dustry has  been  largely  responsible  for  the  advances  in  rare- 
earth  chemistry.  The  mantles  contain  about  99%  of  thoria 
and  about  i%  of  ceria  (Welsbach  Co.  Bulletins  (1907-8)). 

Thorium  carbide  is  said  to  have  been  used  in  filaments 
for  incandescent  electric  lamps,  and  the  oxide  in  electric 
glowers  such  as  the  Nernst  lamp.  Yttria  and  zirconia  are 
better  for  the  latter  purpose  because  they  are  less  volatile. 
Bolton  (Zeitsch.  f.  Electrochem.  xvn,  816)  states  that 
water  which  has  been  in  contact  with  thorium  seems  to 
prolong  the  life  of  certain  animal  organisms,  while  the 
action  upon  vegetable  life  is  injurious. 

Zirconium  has  found  application  in  the  manufacture  of 
the  Nernst  glowers,  about  85%  of  zirconium  oxide  to  15% 
yttrium-earth  oxides  of  the  higher  atomic  weights  being 
used  in  their  manufacture.  The  carbide  of  zirconium  is 
said  to  be  an  excellent  conductor  of  electricity ;  ninety  parts 
of  it  mixed  with  ten  parts  of  the  metal  ruthenium  have  been 
made  into  filaments  for  use  in  the  zirconium  lamp  (Sander, 
Jour.  f.  Gasbel.  XLV  n,  203,  or  Chem.  Zentr.  (1905)  i,  1290; 
Bohm,  Chem.  Ztg.  xxxi,  985,  1014,  1037,  1049).  The  use 
of  zirconium  nitrate  as  a  food  preservative  has  been 
mentioned  (Baskerville,  Eng.  and  Min.  Jour.  LXXXVII, 
548).  Ferro-zirconium  is  finding  some  use  as  a  scavenger 
and  hardening  agent  in  steel  manufacture. 

Zirconium  oxide  has  been  used  as  an  enamel  (Jost,  Ger- 
man Patent  285,981  (1914);  Leuch,  285,344  (1914);  and 
refractory  vessels  which  will  stand  a  temperature  of  2000°  C. 
have  been  made  from  oxides  of  zirconium  and  thorium 
(Knofler,  German  Patent  285,934  (1913);  Arnold,  U.  S. 
Patents  1,121,889  (1914),  1,157.662  (1915);  Weiss  and 
Lehman,  Ztschr.  anorg.  Chem.  LXV,  218).  Zirconia  is  the 


200  THE  RARER  ELEMENTS. 

principal  constituent  of  zirkite,  a  commercial  product  de- 
signed to  withstand  thej  heat  of  high  temperature  furnaces 
(Meyer,  Mineral^Foote-Notes,  Philadelphia,  Mar.-Apr.  1919.) 

Thallium  has  been  used  in  the  manufacture  of  optical 
glass,  and  is  said  to  give  a  higher .  refractive  power  than 
lead  (Lenher,  Electrochem.  Ind.  (1904),  n,  61).  Certain 
compounds  of  thallium  are  being  employed  to  prolong  the 
life  of  the  tungsten  filament  in  incandescent  lamps. 

For  titanium  a  number  of  applications  *  in  the  arts  have 
been  found.  As  ferro-titanium,  an  alloy  containing  from 
30%  to  55%  of  titanium,  it  is  used  in  the  manufacture  of 
steels ;  it  is  said  to  add  greatly  to  their  tensile  strength  and 
elastic  limit.  Titanium-steel  rails f  have  given  excellent 
service  at  the  throat  of  the  New  York  Central  R.  R.  ter- 
minal yard  in  New  York  City,  showing  practically  no 
wear  in  one  year  where  the  life  of  a  rail  had  been  from  six 
to  eight  months.  Titanium  improves  iron  and  steel  by 
unit:n2,  in  the  course  of  manufacture,  with  the  oxygen  and 
nitrogen,  which  pass  off  in  slag ;  the  formation  of  blow-holes 
is  thus  prevented.  Cuprotitanium  is  employed  in  the 
manufacture  of  brass.  The  metal  has  been  used  to  a  certain 
extent  as  a  filament  for  incandescent  electric  lamps.  Ru- 
tile,  titaniferous  magnetite,  titanium  carbide,  and  titanium 
suboxide  are  all  finding  use  as  electrodes  with  carbon  blocks 
in  arc  lamps.  Electrodes  containing  titanium  give  better 
distribution  of  color  and  light,  higher  efficiency,  and  lower 
cost  of  maintenance.  The  electrodes  made  of  the  carbide 
and  of  the  sub-oxide  are  generally  used  as  anodes.  Other 
commercial  uses  of  titanium  are  found  in  the  employment  of 
rutile  for  giving  a  yellow  color  to  porcelain  tile  and  to  arti- 
ficial teeth;  of  titanium  chloride  and  titanous  sulphate  as 
mordants;  and  of  titanous  potassium  oxalate  as  a  mordant 
and  yellow  dye  in  the  treatment  of  leather.  Titanic  oxide 

*  See  Levy,  Chapter  XXII,  foot-note,  page  196. 

t  See  Dudley,  Use  of  Titanium  in  Bessemer  Rails,  Jour.  Ind.  and  Eng.  Chem. 
n,  299. 


SOME    TECHNICAL    APPLICATIONS.  2Oi 

lias  been  used  as  a  protective  paint  for  iron  and  steel,  and 
to  a  limited  extent  as  an  incandescent  medium  for  gas  lights. 
The  ferrocyanide  has  found  employment  as  a  substitute 
for  Schweinfurth's  green  (Baskerville,  Eng.  and  Min.  Jour. 
LXXXVII,  10).  On  combustion  titanium  gives  a  brilliant 
light,  a  characteristic  that  has  led  to  its  use  in  pyro- 
technics. The  nitride  has  been  suggested  as  a  source 
of  nitrogen  for  fertilizers,  for  the  element  combines  readily 
with  nitrogen,  and  yields  ammonia  on  being  heated  with 
hydrogen. 

Vanadium  has  found  employment  in  a  photographic 
developer,  in  a  fertilizer  for  plants,  in  coloring  material  for 
glass,  and  with  anilin  in  a  black  dye.  Vanadyl  phosphate 
has  been  found  to  behave  physiologically  like  potassium 
permanganate  (Ephraim,  Das  Vanadin  und  seine  Verbin- 
dungen,  83).  Vanadic  acid  (V2O5)  is  employed  in  making 
a  waterproof  black  ink  with  tannic  acid,  in  manufacturing 
sulphuric  acid  by  the  contact  process  (Kuster,  Chem.  Zentr. 
(1905)  i,  328),  as  a  substitute  for  gold  bronze,  and  as  a 
catalyzer  to  accelerate  oxidation  processes,  such  as  the 
oxidation  of  sugar  to  oxalic  acid,  of  alcohol  to  aldehyde, 
and  of  stannous  to  stannic  salts  (Naumann,  J.  pr.  Chem. 
(2)  LXXV,  146).  Some  of  the  oxides  have  been  used  in 
ceramic  decoration,  and  the  trioxide  and  chloride  as  mor- 
dants (Baskerville,  Eng.  and  Min.  Jour.  LXXXVII,  518). 
Probably  of  more  importance  than  any  of  the  foregoing 
uses  of  vanadium  is  its  employment  in  the  manufacture 
of  steel,  which  gains  greatly  in  elasticity  and  tensile  strength 
by  the  presence  of  from  .15%  to  .35%  of  this  element, 
introduced  as  ferro-vanadium,  an  alloy  containing  about 
30%  of  vanadium.  (See  pamphlets  by  J.  Kent  Smith, 
Amer.  Vanadium  Co.) 

The  use  of  the  tantalum  filament  as  a  substitute  for 
carbon  was  an  interesting  step  in  the  development  of  incan- 
descent electric  lighting.  The  tantalum  lamp  produces  a 
light  of  one  candle-power  for  every  two  watts  of  electrical 


202  THE    RARER   ELEMENTS 

power,  as  against  three  and  one-tenth  watts  required  by 
the  ordinary  carbon  lamp.  The  tantalum  filament, 
however,  has  now  been  superseded  to  a  great  extent 
by  tungsten.  (Mineral  Resources  U.  S.  1908-1910.) 
The  hardness  of  tantalum  and  its  resistance  to  chem- 
ical action  have  suggested  its  use  in  pens;  and  pure 
or  alloyed  with  iron,  silicon,  boron,  aluminum,  tin,  titanium, 
or  nickel,  it  has  been  used  in  watch  springs,  clock  move- 
ments, anvils,  and  tools  for  cutting  (Baskerville,  Eng.  and 
Min.  Jour.  LXXXVI,  noo;  Siemens,  German  Patent  282,575 
(1913)).  An  alloy  with  gold  and  copper  is  recommended 
for  many  purposes  as  a  substitute  for  gold  (Siemens,  German 
Patent  284,241  (1913)).  Tantalum  has  found  some  use  as 
a  cathode  in  electrolysis,  being  substituted  for  platinum 
(Brunck,  Chem.  Ztg.  xxxvm,  565),  and  as  an  electrical 
resistance  wire  by  coating  it  with  platinum  to  prevent  oxi- 
dation at  high  temperatures  (Simpson,  U.  S.  Patent  1,175, 
693  (1916)).  It  has  been  employed  in  the  manufacture 
of  burnishers  for  use  in  dentistry. 

The  element  niobium  is  said  to  have  found  some  use 
in  the  manufacture  of  filaments  for  incandescent  lamps, 
and  some  of  its  compounds  in  the  preparation  of  mantles 
for  gas  lighting  (Baskerville,  Eng.  and  Min.  Jour.  LXXXVI,  960) . 

Molybdenum  alloyed  with  iron  has  been  used  in  the 
manufacture  of  steel  (Mineral  Resources  U.  S.  1914). 
Molybdenum  wire  is  said  to  have  found  some  use  as  a 
support  for  tungsten  filaments  (Mineral  Resources  U.  S. 
1908-1914).  Ammonium  molybdate  is  an  important  re- 
agent in  the  analysis  of  phosphates.  It  has  also  been 
applied  in  fire-proofing  and  as  a  germicide  and  disinfectant. 
Sodium  molybdate  is  employed  in  coloring  pottery  and 
porcelain,  and  in  dyeing  silks  and  woolens.  Molybdenum 
tannate  with  logwood  extracts  finds  use  in  dyeing  leather, 
and  "  molybdenum  indigo  "  (Mo2O7)  is  a  useful  but  expen- 
sive pigment  for  india  rubber  (Baskerville,  Eng.  and  Min. 
Jour.  LXXXVI,  1055). 


SOME    TECHNICAL    APPLICATIONS.  203 

Doubtless  the  most  interesting  use  of  tungsten  at  present 
is  that  of  its  metallic  filament  in  electric  lighting.*  With 
its  melting-point  of  about  3000°  C.,  this  metal  makes  a 
lamp  which  gives  one  candle-power  of  light  for  every  one 
and  twenty-five  hundredths  watts  of  electrical  power,  as 
against  two  watts  required  by  the  tantalum  lamp;  and 
which  has  a  life  of  one  thousand  or  more  hours,  or  about 
twice  as  long  as  that  of  the  carbon  and  tantalum  lamps. 
A  disadvantage  of  the  tungsten  lamp,  at  first,  was  the 
extreme  fragility  of  the  filament.  Recent  improvements 
in  manufacture,  however,  have  made  feasible  not  only  the 
safe  shipment  of  tungsten  lamps,  but  the  equipment  of 
railroad  trains  and  automobiles  with  them.  Siemens  and 
Halske,  A.-G.,  of  Berlin,  Germany,  have  taken  out  patents 
on  a  process  for  increasing  the  ductility  of  tungsten  by 
adding  8%-2o%  of  nickel. f  The  high  melting-point  of 
the  element  has  suggested  its  possible  use  in  the  manu- 
facture of  crucibles  (Mineral  Resources  U.  S.  1908-1914). 
Certain  salts  are  used  in  weighting  silks.  Sodium  tungstate 
is  employed  in  fireproofmg  draperies,  as  a  mordant  in  dye- 
ing, and  with  potassium  tungstate  in  the  production  of 
magenta  and  saffron  bronzes.  Tungstic  oxide  is  used 
.as  an  oil  and  water  color  (Baskerville,  Eng.  and  Min. 
Jour.  LXXXVII,  203).  Calcium  tungstate,  on  account  of 
its  fluorescence,  is  used  in  the  Roentgen  ray  apparatus; 
lead  tungstate  has  been  substituted  for  white  lead  in  paints. 
Compounds  of  tungsten  have  been  employed  in  coloring 
glass  and  porcelain.  The  alloy  with  aluminum  is  used  in 
French  automobile  construction,  and  the  alloy  with  alumi- 
num and  copper  in  the  blades  of  propellers.  Alloyed  in 
small  percentages  with  steel,  tungsten  is  used  for  the 

*  For  a  full  discussion  of  tungsten,  tantalum,  osmium,  and  zirconium  filaments 
in  electric  lighting,  see  Weber,  Die  elektrischen  Metallfadengluhlampen,  pub.  by 
M.  Janecke,  Leipzig. 

t  For  a  discussion  of  methods  of  preparing  wire,  see  Miiller,  Ztschr.  angew. 
•Chem.  xxvi,  422. 


204  THE    RARER    ELEMENTS. 

following  purposes:  (a)  to  toughen  armor  plate;  (&)  to 
stiffen  car  springs;  (c)  to  increase  the  permanency  of 
magnets ;  (d)  to  increase  the  vibratory  response  in  sounding- 
plates  and  wires  for  musical  instruments;  (e)  to  prevent 
projectiles  and  high-speed  tools  from  losing  their  temper 
when  hot  (Van  Wegenen,  Chem.  Engineer  iv,  217).  Hale 
(Eng.  and  Min.  Jour.  LXXXVII,  813)  states  that  tungsten 
steel  is  poor  shock-resisting  steel,  but  has  great  crushing 
strength.  Tungsten  has  recently  found  many  other  tech- 
nical applications,  e.g.  standard  weights,  acid-proof  dishes 
and  tubes,  pens,  and  knife  blades  (Mineral  Resources  U.  S. 
1914;  Fink,  J.  Ind.  Eng.  Chem.  v,  8;  Mineral  Industry, 
(1914)  759,  1915). 

Uranium  salts  are  used  in  the  production  of  certain 
velvety-black  glazes  for  pottery,  and  of  greenish-yellow 
iridescent  glass.  Uranium  increases  the  strength  of  cast 
iron  or  semi-steel  (Iron  Age,  c  1413,  ci  77).  Mixed  with 
calcium  fluoride,  in  arc  lamps  it  gives  an  intense  snow-white 
light  of  high  photographing  power  (Elect.  World  LXX, 
1002).  The  employment  of  the  carbide  in  filaments  for 
electric  lighting  has  also  been  mentioned  (Baskerville,  Eng. 
and  Min.  Jour.  LXXXVII,  257).  Uranium  acetate  has  been 
used  in  medicine  as  a  precipitant  of  proteids. 

Elementary  selenium  has  the  peculiar  property  of  being 
a  fairly  good  conductor  of  electricity  in  the  light,*  while  in 
the  dark  it  is  practically  a  non-conductor.  This  property 
has  been  made  of  service  in  the  construction  of  electrical 
apparatus  for  automatically  lighting  and  extinguishing  gas- 
buoys,  for  exploding  torpedoes  by  a  ray  of  light,  for  tele- 
phoning along  a  ray  of  light,  for  transmitting  sounds  and 
photographs  to  a  distance  by  telegraph  or  telephone  wire, 
and  for  measuring  the  quantity  of  Roentgen  rays  in  thera- 
peutic applications  (Hess,Mineral  Resources  U.S.  1906-1914). 
Selenium  cells  have  been  constructed  for  measuring  the 

*  Ries  (Physikal.  Ztschr.  xn,  480)  discusses  reasons  for  this  property. 


SOME   TECHNICAL  APPLICATIONS.  205 

intensity  of  light  (Huels,  Bull.  Univ.  Wisconsin,  Madison, 
No.  157,  419).  Selenium  compounds  are  finding  important 
applications  in  the  manufacture  of  red  enamel  ware,  in 
the  enameling  of  steel,  and  in  the  production  of  red  glass 
for  use  in  railroad  signals  (Jour.  Ind.  and  Eng.  Chem.  iv, 
539;  Fenaroli,  Chem.  Ztg.  xxxvin,  177,  873).  The  selen- 
ides  and  organic  compounds  of  selenium  have  been  sug- 
gested for  use  in  making  dyes  (Wasserman,  German  Patent 
286,950  (1913);  Bauer,  Ber.  Dtsch.  chem.  Ges.  XLVII, 
1873).  Sodium  selenite  has  been  employed  to  show  the 
reducing  power  of  bacteria  (Merck's  Index,  1907).  Selen- 
ium has  found  some  use  in  the  vulcanization  of  rubber 
(Jour.  Ind.  and  Eng.  Chem.  x,  117). 

Tellurium  has  shown  certain  peculiar  behavior  toward 
electricity  which  would  indicate  that  some  electrical  uses 
may  be  found  for  the  element  (Hess,  Mineral  Resources 
U.  S.  (1908),  719).  The  tellurides  have  been  mentioned 
as  of  possible  value  in  making  dyes,  as  well  as  in  coloring 
glass  (Wasserman,  loc.  cit.,  Fenaroli,  loc.  cit.).  Tellurium  is 
said  to  have  some  use  in  forming  high-resistant  alloys,  and 
in  medicine  as  an  antisudorific  agent. 

The  element  platinum  is  finding  increasing  use  in 
jewelry,  and  continues  to  be  important  in  the  manufacture 
of  chemical  apparatus.  Recently  2000  kilos  were  reported 
as  having  been  used  in  one  year  in  the  production  of  pins 
for  artificial  teeth.  Its  application  in  the  sulphuric  acid 
contact  process  is  most  important.  The  use  of  platinum 
in  electrical  industries  is  gradually  becoming  less,  on  account 
of  the  substitution  of  nickel-chromium  alloys,  molybdenum, 
and  tungsten  (Mineral  Resources  U.  S.  (1914),  338). 

Iridium,  alloyed  with  osmium,  is  employed  for  compass- 
bearings  and  for  tips  of  gold  pens.  Its  alloy  with  platinurn 
is  used  in  the  manufacture  of  laboratory  apparatus  and 
for  standard  weights  and  measures.  The  black  oxide 
finds  use  in  china-painting. 

Osmium  has  long  been  employed  as  a  stain  in  micro- 


fl06  THE  RARER  ELEMENTS. 

scopic  work,*  and  more  recently  as  a  filament  for  incan- 
descent lamps  (Jour.  f.  Gasbel.  XLIV,  101;  XLVIII,  184' 
Chem.  Zentr.  (1907)  n,  433). 

Palladium,  because  of  its  hardness  and  unalterability  in 
air,  is  used  for  graduated  surfaces  of  fine  apparatus.  It  has 
also  found  use  in  alloys  for  dental  work,  and  on  account  of 
its  comparatively  low  fusing-point  it  is  employed  in  solder- 
ing the  other  platinum  metals. 

Rhodium  alloyed  with  platinum  (10%  of  Rh)  has  been 
used  in  making  thermo-elements  for  high-temperature  work. 

Ruthenium,  as  has  been  already  stated,  has  been  mixed 
with  zirconium  carbide  for  use  in  the  filament  of  the  zir- 
conium lamp. 

The  uses  of  gold  in  coinage,  in  jewelry,  and  in  dentistry 
need  no  description. 

i  An  interesting  application  of  helium  was  worked  out  in 
connection  with  recent  war  activities,  viz.:  its  use  in  bal- 
looning (Eng.  and  Min.  Jour.  Feb.  8,  1919,  p.  273).  This 
gas  has  about  92%  of  the  buoyant  effect  of  hydrogen  and  is 
non-inflammable.  A  cheap  process  for  its  extraction  from 
natural  gas  has  brought  down  the  estimated  cost  from 
$1700  to  10  cents  a  cubic  foot.  At  the  close  of  hostilities 
147,000  cubic  feet  of  nearly  pure  helium  stood  ready  for 
shipment. 

*  Schultze,  Zeitsch.  f.  wiss.  Microskop.  xxvn,  465. 


CHAPTER  XIII. 

THE  QUALITATIVE  SEPARATION  OF  THE  RARER 
ELEMENTS. 

The  following  schemes  of  separation  will  give  some 
idea  of  the  problems  of  qualitative  analysis  in  the  presence 
of  some  of  the  rarer  elements.  None  of  the  schemes  given 
considers  the  possible  presence  of  all  of  these  elements. 

Tables  I  and  ITf  include  original  methods  which  have 
given  fairly  satisfactory  results  in  the  hands  of  the 
author's  classes. 

Tables  II,  VI,  and  VIII,  together  with  a  considerable 
part  of  the  material  contained  in  the  accompanying  direc- 
tions and  notes  were  prepared  from  the  publications  of 
A.  A.  Noyes  and  his  associates,  to  whom  the  author  acknowl- 
edges his  indebtedness.  No  attempt  has  been  made  here  to 
take  up  the  study  of  the  separation  methods  in  detail,  nor 
to  indicate  the  processes  used  for  the  separation  of  the 
commoner  elements  from  one  another  when  the  rarer 
elements  are  not  involved.  All  these  processes  are  fully 
discussed  in  the  original  papers,  to  which  reference  is 
made. 

Tables  IV  and  V  offer  processes  worked  out  by  James, 
but  rather  beyond  the  scope  of  any  but  advanced  students. 
They  have  been  added,  however,  without  explanatory 
notes,  merely  to  show  the  best  methods  of  attack  on  the 
complicated  problem  of  rare  earth  analysis;  and  references 
to  the  original  papers  have  been  furnished. 

207 


208  THE  RARER  ELEMENTS. 

In  Table  VII  the  method  suggested  by  Bohm  has  been 
put  into  diagrammatic  form.  In  this  scheme  no  attempt 
was  made  by  Bohm  to  give  anything  further  than  a  process 
for  the  separation  of  the  more  important  rare  earths  from 
other  elements  and  from  one  another.  To  make  the  table 
more  complete,  however,  methods  for  the  separation  of 
the  other  rare  elements  mentioned  have  been  supplied. 


THE  ALKALI  GROUP. 

Before  taking  up  the  analysis  as  outlined  in  Table  I, 
the  student  is  advised  to  review  by  means  of  the  following 
experiments  the  reactions  of  the  elements  involved,  and  to 
put  the  results  into  tabular  form.  Use  solutions  of  the 
chlorides  of  Li,  Na,  K,  Rb,  and  Cs,  respectively.  Perform 
the  experiments  upon  separate  portions  of  these  solutions. 
(i)  Addition  of  solution  of  H2PtCl6;  (2)  of  Na3Co(NO2)6; 
(3)  evaporation  with  A^CSO^s+H^SCV,  (4)  dehydration 
of  chlorides  with  amyl  alcohol;  (5)  review  of  flame  and 
spectroscopic  tests. 


THE  QUALITATIVE  SEPARATION. 


209 


THE  QUALITATIVE  SEPARATION. 

TABLE  I. 

The  alkalies  present  as  chlorides.* 
Dissolve  about  1-5  grms.  of  the  mixed  salts  in  water,  and  dehydrate  with  amyl 


alcohol. 


R 


Na,  K,  Rb,  Cs. 
Dissolve  in  a  few  drops  of  water, 
add  H2PtCl6. 


Li.  Confirm  by  spectroscope. 


CsRb(K)  as  chloroplatinates. 

(1)  Test  a  portion  of  the  precipitate  on  a  plat- 
inum wire  before  the  spectroscope. 

(2)  Decompose  by  gentle  ignition,  add  a  few 
drops  of  water  and  filter,  add  a  little  solid 
aluminum  sulphate,  dissolve  and  crystallize. 
CsAl(SO4)2  •  1 2H2O  crystallizes  before 
RbAlSO4  •  1 2H2O.     See  page  1 2. 


K,Na.  Add  an  equal  volume 
of  alcohol.  Filter,  and  wash 
with  water  and  alcohol  (i-i). 


K.     Confirm  by  spectroscope. 


Na.  Add  a  few  drops  of  a  one- 
per  cent,  solution  of  H2SO4  in 
alcohol.  Ppt.  Xa2SO4.  If  no 
precipitate  forms  saturate 
with  HC1  gas.  Ppt.  XaCl. 


*  If  the  alkalies  are  present  as  salts  of  mixed  volatile  acids,  they  may  be  con- 
verted to  the  sulphates  by  evaporation  with  H2SO4  to  the  fuming-point.  The  sul- 
phates may  be  converted  to  the  carbonates  by  treating  with  an  excess  of  Ba(OH)2 
in  solid  form,  filtering  off  the  BaSO4  and  insoluble  excess  of  Ba(OH)2,  and  removing 
the  Ba(OH)2  in  solution  as  insoluble  BaCO3  by  passing  CQ2  and  boiling.  The 
alkalies  are  left  in  solution  as  carbonates,  from  which  form  they  may  easily  be 
converted  to  any  salt  desired. 


210  THE  RARER  ELEMENTS. 

II 

THE  ALUMINUM  AND  IRON  GROUP. 

Before  beginning  work  upon  this  analysis  the  student 
should  review  the  reactions  of  the  elements  involved. 
The  common  elements  Fe  and  Al  are  included  in  the  exper- 
iments suggested,  as  they  are  typical  members  of  their 
respective  subdivisions. 

Upon  separate  solutions  of  the  following  salts:  FeCl3, 
TiCl4,  T1C13,  ZrCU,  A1C13,  BeCl2,  UO2C12  and  NaVO3 
perform  the  following  experiments,  and  record  the  results 
in  tabular  form:  (i)  Add  HC1+H2S;  (2)  add  NH4OH  + 
(NH4)2S  to  the  product  of  (i);  (3)  add  NaOH+Na2O2 
to  an  HC1  solution  of  any  precipitate  obtained  in  (2); 
(4)  add  NH4OH  to  portions  of  the  original  solutions;  (5) 
warm  solutions  of  the  Al,  V,  Be,  and  U  salts  in  a  closed 

bottle    with    NaHCOs;     (6)    shake    separate    portions    of 

in  in 

HQ(i.ia)  solutions  of  the  hydroxides  of  Fe,  Ti,  Zr  and  Tl 
with  ether  in  a  separation  funnel,  and  test  the  resulting 

layers;  (7)  dehydrate  the  chlorides  of  Fe,  Ti,  Zr  and  Tl 
with  amyl  alcohol;  (8)  add  NaHP04  to  solutions  of  Ti 
and  Zr  salts  in  presence  and  absence  of  H2O2;  (9)  add 

Na2SO3  followed  by  KI  to  solutions  of  Tl  and  Fe  salts; 
(10)  add  strong  HC1  to  concentrated  solutions  of  chlorides 
of  Be  and  Al;  (n)  dehydrate  concentrated  solutions  of  the 
nitrates  of  Be  and  Al  with  amyl  alcohol;  (12)  add  NaHPO4 
to  solutions  of  U  and  V  salts. 

DIRECTIONS  AND  NOTES  FOR  Al  AND  Fe  GROUP. 

Boil  out  H2S  if  present.  Add  NH4OH  in  distinct  but  not  large 
•excess;  note  precipitate;  pass  H2S  to  saturation,  warm,  filter,  wash 
with  dilute  (NH4)2S  and  then  with  water.  Avoid  the  use  of  (NH4)2S 
as  precipitant  because  of  its  solvent  action  upon  Ni.  Transfer  the  pre- 
•cipitate  with  5-20  cm.3  of  HC1  (1.12).  Stir  before  warming,  then  boil 
•a  few  minutes.  If  a  black  residue  remains  add  a  few  drops  of 


THE   QUALITATIVE  SEPARATION.  211 

(1.42)  and  boil.  Evaporate  nearly  to  dryness  with  HN03  to  remove 
HC1.  Dilute  to  10-20  cmT3,*  make  alkaline  with  NaOH,  add  water 
to  double  the  volume  of  the  liquid.  Add  gradually  0.5-3  grms.  of 
Na2O2  with  stirring.  Add  5  cm;3  of  10%  Na2CO3,  unless  it  is  known  that 
the  alkali  earths  are  absent;  boil  to  remove  excess  of  Na202.  Cool,  add 
equal  volume  of  water,  and  filter. 

HC1  is  added  before  HN03  to  avoid  oxidizing  effect  of  HN03  and 
-  formation  of  H2SO4,  which  in  turn  interferes  with  test  for  Cr04  by  Ba 
and  Pb  salts.  HNO3  is  necessary  to  dissolve  sulphides  of  Ni,  Co,  and 
V.  HC1  must  be  removed  by  evaporation,  because  chlorides  interfere 
with  test  for  CrO4  by  Pb.  If  (NH4)2S  precipitate  is  allowed  to  stand 
for  some  time  before  treating  it  with  acid,  or  if  the  mixture  is  heated 
a  long  time  after  precipitation,  ZrO(OH)2  and  TiO(OH)2  tend  to  remain 
undissolved  after  treatment  with  acids,  because  of  partial  dehydration. 
These  compounds  may  be  dissolved  by  HF  in  Pt  dish,  and  HF  removed 
by  evaporation  with  HN03  or  HC1.  Na2O2  oxidizes  Fe,  Mn,  Co,  Ni, 

Tl,  Cr,  and  U.     U  goes  into  solution  as  peruranate. 

Al  GROUP. — To  the  filtrate  from  the  Na202  precipitate  add  HN03 
(1.20),  keeping  the  solution  cool  until  it  reacts  faintly  acid.  Dilute 
the  solution  to  100  cm3;  transfer  to  a  flask,  and  place  a  funnel  in  the 
mouth  of  the  flask.  Add  NaHC03  until  the  mixture,  on  shaking,  no 
longer  turns  litmus  red  at  once,  and  add  about  1-5  grms.  of  solid 
NaHCOs.  Warm  20-30  minutes  on  a  water  bath.  Cool  and  filter. 

Alkaline  solution  is  kept  cool  during  neutralization  to  avoid  reduction 

VI  III 

of  Cr  to  Cr  salt.  Care  must  be  taken  to  keep  strictly  to  the  directions 
about  the  use  of  NaHC03.  Stronger  solutions  dissolve  Be. 

Dissolve  the  precipitate  in  dilute  HC1  and  add  NH4OH  in  moderate 
excess.  Heat  to  boiling,  filter,  and  wash  thoroughly.  Dissolve  the 
precipitate  in  dilute  HNO3,  evaporate  to  a  few  crrT3,  and  dehydrate 
with  amyl  alcohol.  Be  dissolves.  To  the  filtrate  from  the  NaHCO, 
treatment  add  HNO3  (1.20)  until  the  solution  is  distinctly  acid  but  not 
in  excess.  If  the  solution  is  colorless,  Cr  is  absent,  and  the  treatment 
with  Pb  salt  and  H2S  may  be  omitted.  If  Cr  is  absent  neutralize  the 
acid  with  NH4OH,  add  acetic  acid,  1-2  grms.  of  (NH4)2S04,  2  grms. 
of  Na2HP04,  and  heat  to  boiling.  Filter,  and  wash  with  a  solution 

*  If  rare  earths  are  to  be  tested  for,  treat  this  solution,  only  faintly  acid 
with  HNO3,  with  NaF  to  complete  precipitation  of  fluorides  of  rare  earths 
Filter  and  reserve  precipitate  for  rare  earth  analysis.  Continue  with  jfiltrate  as 
directed  above. 


212  THE  RARER   ELEMENTS. 

of  (NH4)2S04.  Dissolve  in  dilute  HC1,  evaporate,  add  NaCl  and 
K4FeC6N6.  Dark  red  =  U. 

Neutralize  the  nitrate  from  the  NaHPO4  nitrate  with  NH4OH  in 
slight -excess  and  saturate  with  H2S.  Pink  or  violet  =  V. 

Fe  GROUP. — Dissolve  the  Na^i  precipitate  in  5-30  dmT3  of  dilute 
HC1,  warm,  filter  off  paper,  etc.,  and  evaporate  to  about  2  cm.3  Add 
about  5  cmT3  of  strong  HN03;  and  boil  to  remove  HC1.  Add  5-20  cmT3 
of  strong  HNO3  and  boil,  adding  0.5  gnn.  of  KC1O3.  Filter  off  the 
MnO2  on  glass  wool  or  asbestos. 

HC1  is  used  rather  than  HNO3  because  HN03  does  not  dissolve 
Mn02  readily.  HC1  is  removed  by  HNO3  because  HC1  dissolves  Mn02. 

If  phosphates  are  absent  (if  present  use  acetate  method)  add  NH4OH 
in  distinct  excess  to  the  nitrate  from  the  Mn02,  filter,  wash,  and  remove 
the  water  present,  by  suction  if  necessary.  Dissolve  in  HC1  (1.12), 
being  careful  to  use  this  strength  of  acid.  Add  to  the  cold  solution 
an  equal  volume  of  ether,  and  shake  in  a  separation  funnel.  Draw  off 
the  layers,  and  repeat  this  operation  with  the  water  layer  until  the 
ether  layer  remains  colorless. 

The  extraction  of  FeCl3  is  most  complete  when  the  acid  is  1.12.  The 
absence  of  FeCl3  from  the  ether  layer  may  be  shown  by  lack  of  color. 
The  water  layer  may  have  yellow  color  due  to  TiO3.  Phosphoric  acid 
does  not  interfere  with  the  separation. 

Evaporate  the  ether  extract  on  a  water  or  steam  bath,  dissolve  the 
residue  in  a  little  dilute  H2S04  and  water.  To  the  cold  solution  add 
a  little  KI  solution  and  Na2S03  until  iodine  color  has  disappeared.  Yellow 
Til  indicates  Tl.  Confirm  by  green  flame.  Evaporate  the  water  layer 
on  a  steam  bath  until  the  ether  is  expelled.  Add  dilute  H2SO4  and 
evaporate  to  the  fuming-point.  Cool,  add  5  crnl3  of  water,  10  cIJI3  of 
3%  H202,  and  10  cm:3  of  10%  Na2HPO4  solution.  Orange-red  color- 
ation =Ti;  white,  flocky  precipitate,  ZrOHPO4=Zr.  Allow  the  mixture 
to  stand  about  an  hour  before  filtering.  If  filtrate  is  still  colored,  add 
powdered  Na2SO3  until  the  color  bleaches.  Precipitate,  white,  flocky 
TiOHP04=Ti. 

The  precipitation  of  the  phosphate  of  Zr  is  slow,  so  that  some  time 
should  be  allowed  for  it  to  form.  The  oxidation  with  H202  is  necessary 
to  keep  the  Ti  from  precipitating  with  the  Zr.  If  rare  earths  are  present 
they  should  be  removed  by  HF  before  testing  for  Ti  and  Zr, 


THE   QUALITATIVE  SEPARATION. 


213 


neutr 
(N0 


sol 


IS     «fi  JJ 

»-*  1**£g 

,  ffi  = 

^^f  *IM 

5-       ~2   sR 


II 

s  I  w 

d 
y 


w    tn  u-a  v 


a.g 


l 


^  "3    rt  TJ     W 

0  ffi  fc  8  •§ 


|9 


?^. 

.2   jfS 


Sffi^Z 


C 


pwffl 
O 


214  THE  R4RER  ELEMENTS. 

A  modification  of  the  method  described  in  Table  II  as 
applied  to  the  separation  and  detection  of  iron,  thallium, 
zirconium,  and  titanium,  starting  with  the  hydroxides.* 

Dissolve  hydroxides  in  the  least  possible  amount  of 
H2SO4.  Treat  with  H2O2,  a  red  coloration  indicating  titan- 
ium. Treat  with  Na2HPO4  in  the  presence  of  NaOHf  and 
add  H2SO4  to  acidity. 

Pf—  — IF 

ZrOHPO<  Treat  with  NaOH. 

P| — |F 

Fe  /  as  hydroxides  Treat  with  H2SO4,  Na2S03  and 

Tl  \  or  phosphates.  Na2HPO4,  and  filter. 

Dissolve  in  H2SO4.    Treat  with  |P 

Na2S03+KI  and  filter.  TiOHPO, 


P—  — |  F 

Til  BoU  to  remove  SC>2,  add  HA  to  break 

up  iodide,  boil  to  remove  iodine,  add 
KSCN.     Red  coloration  indicates  Fe. 

*  Browning,  Simpson,  and  Porter,  Am.  Jour.  Sci.  XLII,  106. 

t  This  step  is  to  prevent  the  excess  of  acid  when  sodium  phosphate  is  added 
acidity  interfering  with  the  ready  precipitation  of  zirconium  phosphate.  Gentle 
warming  after  the  addition  of  sodium  hydroxide  gives  good  results,  but  in  no  case 
should  the  solution  be  boiled,  and  if  warmed  it  should  be  cooled  and  treated  with 
hydrogen'dioxide  before  acidifying  with  sulphuric  acid. 


THE  QUALITATIVE  SEPARATION.  215 

III 

THE  RARE  EARTH  GROUP. 

Before  taking  up  the  analysis  indicated  in  Table  III 
the  student  is  directed  to  review  the  reactions  of  the  ele- 
ments involved,  and  to  put  the  results  in  tabular  form. 

Upon  separate  solutions  of  the  following  salts,  Y(N03)3, 
Ce(N03)3,  Pr(N03)3,  Nd(NO3)3,  La(N03)3,  Ce(NO3)4  and 
Th(NO3)4,  try  the  action  of  the  following  reagents  in  solution : 
(i)  NaOH,  NH4OH,  or  KOH:  (2)  Na2CO3  or  K2C03;  (3) 
(NH4)2C03;  (4)  H2C204;  (5)  (NH4)2C2O4;  (6)  NaF; 
(7)  Na2S^03,  and  warm;  (8)  H2O2;  (9)  K4FeC6N6;  (10) 
Na2HPO4;  (n)  KIO3;  (12)  K2CrO4;  (13)  sebacic  acid; 
(14)  Cl  or  Br  upon  the  suspended  hydroxides;  (15)  K2S04 
to  saturation.  Try  also  the  action  of  acetic  and  dilute 
hydrochloric  acids  upon  the  precipitates  formed  in  (i),  (2), 
(4),  (10),  (n),  and  (12),  and  the  action  of  H202  upon  the 
hydroxides. 

TABLE  III. 

If  rare  earths  are  to  be  tested  for,  treat  the  hydrochloric  acid  solution  of  the 
Fe  and  Al  group  precipitate  with  NaF.*  This  precipitates  the  fluorides  of  the 
rare  and  possibly  the  alkali  earths.  The  precipitate  should  be  thoroughly  washed, 
and  evaporated  with  H2S04  to  decompose  the  fluorides.  This  process  removes 
the  alkali  earths  as  insoluble  sulphates.  The  solution  containing  the  sulphates 
of  the  rare  earths,  with  excess  of  H^SOi  removed,  is  treated  with  NajSzOj,  and 
warmed. 


PI 

Th(S203)2. 
Dissolve  in  HC1. 
Precipitate  with  H2C2O4, 
wash  thoroughly. 
Dissolve   in    (NH4)2C2O4, 
acidify  with  HC1. 
P  confirms  Th. 

|F 
Ce  and  Y  earths. 
Saturate  with  Na2S04. 

P| 

*Ce2(S04)3-;yNa2S04. 
Decompose  with  NaOH,f 
and  add  H2O2. 
Reddish  yellow  =  Ce.f 

|F 

Add  NH4OH;  white  P, 
which     dissolves    in 
acid,  and  is  pptd.  by 
(NH4)2C204=Y. 

*  Noyes,  Bray,  and  Spear  evaporate  the  HC1  solution  of  the  Al  and  Fe  group  to  dryness 
and  treat  with  HF.  They  state  that  the  fluorides  of  Al  and  Cr  are  somewhat  insoluble  m 
HF,  and  that  Ti  and  Zr,  if  present,  tend  to  retain  HF. 

t  The  double  sulphates  may  be  conveniently  decomposed  by  fusion  with  an  equal 
weight  of  pure  charcoal  (sugar  carbon)  in  a  porcelain  crucible.  The  residue  after  fusion, 
consisting  mainly  of  sulphides,  dissolves  readily  in  dilute  HC1  (Browning  and  Blumentdai, 
Amer.  Jour.  Sci.  [4]  xxxn,  164). 

J  If  the  presence  of  other  Ce  earths  is  suspected,  they  may  be  removed  from  Ce  by 
treating  the  hydroxides  suspended  in  a  solution  of  NaOH  with  Cl  or  Br.  These  earths 
dissolve,  leaving  CeOa. 


216  THE  RARER  ELEMENTS. 

TABLE 

CHLORIDES  OF  La,  Ce,, 


(1)    Ppt,  La,  Pr,  Nd,  Sm,  Eu,  Gd  &  traces  of  Tr,  Dy,  etc, 
double  Na  sulfates.    Convert  into  nitrates  and  boil  with  KBr  03 
and  Ca  C03. 


(3)  Ppt  basic 
nitrate  of  Ce 


(4)   Solution  pptd  by  oxalic  acid 
Transform  oxalates  into  double  Mg 
.nitrates  and  fractionate 


3    "8 
3 


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J    'S3 
*    5 


(11  a)  Pr  XH4  nitrates 
La  &  Pr  Ppt  by  oxalic  acid. 

Pr  oxalate 


*  This  diagram,   published   by  James   in    1912    (Jour.    Amer.  Chem.  Soc.,  xxxiv,  757) 
of  Th  and  Zr.     For  descriptive  details  see  original  article. 

[By  permission  of  the  Journal  of 


THE   QUALITATIVE  SEPARATION. 


217 


(2)  Solution  ppfd  by  oxalic  acid  Tr,  Dy,  Ho  Yt  'Er  T.m 
-Yb,  Lu&  Ct  with  traces  of  Sc,  Gd,  En,  &  Sm  oxalates  Converted 
sjnto  bromates. 


(16)  Gd,  Tr,  &Dy 
titrates.  Convert  into 
double  Ni  nitrates 


(18)  Double    (.24)  Tr,  Dy    (28)  Tr,  J)y  (29)  £$^(30)  Ho  &  Yt 


ethyl- 
sulfate: 


ethyl-sulfates 
Fuse  nitrates 


nitrate  of        &  Gd  ethyl- 

&  Gd          Ni  nitrates     sulfates 

Crystallize  simple 
nitrates  with  Bi-mtrate 

-^  ^  (31)  Nitrate  (32)  Yt&  Ho 

&  Tr  (25)  Tr    itrate  (27)Dy  &  Tr  of  Ho          nitrates 
nitrates  nitrates 

brings  the  problem  of  rare  earth    separation  to  date.      It  assumes  the  previous  removal 
the  American  Chemical  Society  and  the  Author.} 


218 


THE  RARER  ELEMENTS 


TABLE  V.' 


*  This  diagram,  published  by  C.  James  in  1908  (Jour.  Amer.  Chem.  Soc.,  xxx,  979)  will 
serve  to  give  a  satisfactory  idea  of  the  best  methods  in  use,  at  the  time  of  its  publication, 
for  the  detailed  separation  of  the  rare  earths.  For  details  reference  is  made  to  the  original 
paper. 


THE  QUALITATIVE  SEPARATION.  219 

IV. 

SILVER,  COPPER  AND  TIN  GROUP. 

Before  taking  up  the  analysis  outlined  in  Table  VI, 
the  student  is  directed  to  review  the  reactions  of  the  rare 
elements  involved.  Lead,  mercury,  and  arsenic  are  included 
for  purposes  of  comparison.  Taking  separate  portions  of 
solutions  of  the  following  compounds,  Pb(N03)2,  T1NO3, 
HgCl2,  AuCl3,  H2PtCl6,  H2Se03,  H2TeO3,  K3AsO3,  and 
(NH4)2MoO4,  make  the  following  experiments,  and  record 
the  results  in  tabular  form:  (i)  Add  HC1;  (2)  add  hot 
water  to  any  precipitate  formed  in  (i);  (3)  add  H2S04 

to  solutions  of  Pb  and  Tl  ;  (4)    add  KI  to  solutions  of  Pb 

i 
and  Tl  ;    (5)  add  H2S  to  separate  solutions  of  all  the  salts 

mentioned  above;  (6)  add  (NH4)2S  to  all  sulphides  pre- 
cipitated in  (5);  (7)  add  HNO3(i:3)  to  the  sulphides  of 
Hg,  Pb,  Pt,  and  Au ;  (8)  add  Br  water  and  KC1  to  the  sul- 
phides of  Hg,  Pt,  and  Au;  (9)  add  NaOH  and  H2C2O4 
to  solutions  of  Au  and  Hg  and  warm;  (10)  acidify  with  HC1 
the  sulpho  salts  of  As,  Pt,  Au,  Se,  Te,  and  Mo;  (n)  add 
HC1,  then  KC1O3  to  the  sulphides  of  As,  Pt,  Au,  Se,  Te,  and 
Mo;  (12)  add  HC1,  then  Na2SO.-<  to  solutions  of  Se,  Te,  and 
Mo;  (13)  add  KI  to  solutions  of  Te  and  Mo;  (14)  to  a  solu- 
tion containing  Mo  add  Zn+KSCN  and  enough  HC1  to 
start  evolution  of  H2. 

DIRECTIONS  AND  NOTES  FOR  Ag,  Cu,  AND  Sn  GROUP. 

Add  4  cm".3  of  HC1  (dilute).  Filter,  wash  with  cold  water  (about 
10  cnf3).  Test  the  filtrate  for  traces  of  Tl  and  Pb. 

PbCl2  and  T1C1  are  somewhat  soluble  in  cold  water  (20-40  mgs.  of 
PbCl2  and  5-15  mgs.  of  T1C1  may  remain  in  solution).  The  solubility 
of  these  chlorides  in  water  is  decreased  by  the  presence  of  HC1  in 
moderate  amount. 

Ag  GROUP.— Treat  the  precipitate  of  AgCl,  PbCl2,  and  T1C1  with 
10  cmT3  of  boiling  water,  pouring  it  back  and  forth  several  times. 
Treat  the  hot  water  extract  containing  Pb  and  Tl  with  one-fifth  its  volume 


220  THE  R4RER  ELEMENTS. 

of  strong  H2S04,  allow  to  cool  and  stand  a  few  minutes.  Wash  with, 
dilute  H2SO4,  since  PbS04  is  slightly  soluble  in  water.  To  the  solution 
containing  Tl  add  2-3  cm:3  of  i%  KI.  If  free  I  appears,  add  H2S03. 
Yellow  T1CI  indicates  Tl. 

Til  is  more  insoluble  than  T1C1.     Its  solubility  is  decreased  by  KI. 
i  in  in 

Tl  is  oxidized  to  Tl  by  Cl,  Br,  I,  and  aqua  regia.     Tl  is  reduced    by 

i  in 

H2SO3.     Tl  is  slightly  oxidized  by  HN03.     Tl  is  not  precipitated  by  HC1. 

Cu  AND  Sn  GROUP. — Before  adding  H2S  see  that  the  volume  of  the 
solution  is  about  40  cmT3  of  which  4  cmT3  is  HC1  (i  .  12).  Heat  the  solu- 
tion to  boiling,  and  saturate  with  H2S.  Use  a  flask  fitted  with  stoppe-i 
and  delivery  tubes,  so  that  gentle  pressure  can  be  obtained.  After 
saturating,  add  equal  volume  of  water,  cool,  saturate  again. 

V 

H2S  is  passed  at  boiling  temperature  for  As,  Pt,  and  Mo.  Pressure 
is  used  to  precipitate  Pt  metals  and  Mo.  The  small  volume  of  liquid, 
40  ciru3,  is  to  keep  Ti,  Bi,  and  Sb  from  precipitating  as  hydroxides  or 

basic  salts,  and  to  precipitate  As  more  readily.     The  final  dilution  and 

ii 
cooling  is  to  precipitate  all  of  the  Cd,  Pb,  and  Sn. 

Digest  precipitate  with  10-20  cm.3  of  (NH4)2S,  add  equal  volume 
of  water,  filter,  and  wash. 

MoS2-s  dissolves  in  moderate  amount  of  (NH4)2S  and  gives  a  deep 
orange-red  color  to  solution.  Its  presence  in  Cu  Group  does  not  inter- 
fere. PtS2  is  not  completely  dissolved  by  (NH4)2S. 

Cu  GROUP. — Add  10-20  crnT3  HNO3  (one-third  strength),  boil  gently 
a  few  minutes.  Dissolve  residue  in  10-40  cm.3  of  saturated  bromine 
water.  Cover  dish  and  warm  5-10  minutes.  Expel  excess  of  bromine, 
add  0.5  grm.  KC1, 1-2  cmT3  HC1  (i  .  12).  Evaporate  until  KC1  crystallizes, 
cool,  add  water  until  KC1  dissolves.  Filter,  wash  with  KC1.  Yellow 
K2PtCl6  =  Pt.  Dissolve  in  hot  water,  test  by  KI.  Make  filtrate 
alkaline  with  10%  NaOH,  add  saturated  solution  of  H2C204  to  acidity, 
dilute  to  15  crru3  and  warm  10-15  minutes  on  steam  bath.  Purple  or 
dark  yellow =Au. 

K2PtCl6  is  much  less  soluble  in  KC1  than  in  water.  Color  with  KI 
due  to  K2PtI6.  Au  is  precipitated  readily  by  H2C204  only  when  solution 
is  slightly  acid  and  hot.  Precipitation  takes  place  slowly. 

Sn  GROUP. — Dilute  the  (NH4)2S  solution,  acidify  with  HC1  and  warm 
gently;  drain  as  dry  as  possible  on  a  filter  and  warm  with  HC1  (i  .  20), 
which  removes  Sn  and  Sb.  Warm  with  5-10  c.n.3  HC1  (i  .  12),  add 
a  little  KC1O3,  evaporate  to  2  cm".3,  or  until  KCi  crystallizes  out  (see 
test  for  Pt,  Cu  Group).  After  removing  Pt,  remove  As  by  NH4OH 
and  MgCl2  mixture.  To  the  filtrate  add  some  H2C204,  boil  out  NH,, 


THE  QUALITATIVE  SEPARATION*  221 

make  slightly  acid  with  H2C204,  and  test  for  Au  as  in  Cu  Group.  Evap- 
orate nitrate  from  Au  nearly  to  dryness,  add  10  cm?  HC1,  and  if  KC1 
separates  filter  it  off.  Add  0.2  grm.  Na2SOa  and  allow  to  stand  a  few 
minutes,  adding  more  NaS03  if  odor  of  S02  is  not  distinct.  Red  Se  =  Se. 

Reaction  more  delicate  in  cold  because  red,  not  black,  Se  forms. 
Te  is  reduced  by  Na2S03  if  HC1  is  much  more  dilute  than  1.12. 

Dilute  nitrate  from  Se,  add  equal  volume  of  water,  a  little  KI 
solution,  and  Na2SO3.  Black  Te  =  Te.  Filter  after  a  few  minutes. 

KI  is  added  because  TeI4  is  more  readily  reduced  by  S02  than  is 
TeCl4.  Molybdic  acid  is  slowly  reduced  by  HI  with  liberation  of  I; 
therefore  Te  should  be  filtered  off  before  confused  with  this  color. 

Boil  filtrate  from  Te  until  S02  is  expelled.  Add  a  little  10%  KSCN 
and  some  Zn.  Red  color  =  Mo. 

The  S02  is  boiled  out  to  avoid  precipitation  of  S  by  Zn.  Long  con- 
tinued action  of  Zn  will  cause  bleaching  of  red  color. 


THE  RARER  ELEMENTS. 


II 

UK 


i  -2 

5  1 


U] 

1 

1 

0 

rt 

Pu  j=  _r 

51 

fis 

e3  O    5 

Itl 

»  c  — 
?H^| 

I* 

ra4OH,  NH4C1,  a 

IF 
Heat  with  H2C2C 

*  1°  ' 

1 

H-4 

—  i 

< 

^|l|  i 
«  »  «  i 

.s 

rfo  *        ^  e  2 

^_| 

1 

1  1 

J3 

<!  "^  2 

X 

cL 

w       *-• 

<1^ 

•N  >    o 

rt 

o     *""* 

to 

*T3 

Qj  "o    03"* 

-j 

5  •- 

i 

3 

4s  * 

^5    1 

M 

"G     a 

O 

M 

| 

9 

rt 

*.  £ 

1          S 

£.              -f 

^r. 

^        I  1 

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2 

8     *u-     *&  S5 

(/}                  PH_.^                        HH        ^ 

sr3 

5T«                     1    | 

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a 

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£                                   *  2 

P4                                                                               1«B 

—        Oc 

3 

S 

It 
jj 

n 

r  and  Tin  Gro 
Id  (NH4)2S. 

rfd 

1 

ill  8o-, 

Q.q3    U             Srt  CT  ^ 

111  ^ 

NP 

ii 

•g-s  g 

-M     c  a 

1 

*<  -o                         ~               ^  6  "I 

<  §rt 

If1 
^                  j  ii 

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y                         1  11 

!fr 

ifli 

cio| 

ifil 


THE   QUALITATIVE  SEPARATION.  223 

Modification  of  the  method  described  in  Table  VI  as 
applied  to  the  separation  of  platinum,  gold,  selenium,  tel- 
lurium, arsenic,  and  molybdenum.* 

The  filtrate  from  the  K2PtCl6  (see  previous  page)  should 
be  made  faintly  alkaline  with  NaOH  and  the  Au  precipi- 
tated either  by  H2C>2  or  by  acidifying  with  oxalic  acid  and 
warming.  The  Se  is  precipitated  as  in  Table  VI. 

Treat  filtrate  with  Na2SO3+KI. 

P—  — [F 

Te  Treat  by  boiling  to  remove  the  SO2,  by 

H2O2  to  break  up  the  iodide,  by  boiling 
to  remove  iodine,  by  excess  of  NaOH 
and  H2O2  to  oxidize  the  arsenic  to 
arsenate,  by  acidifying  to  remove  ex- 
cess of  NaOH,  by  NH4OH  and  MgCl2 
mixture,  and  nitration. 


PT~  ~F 

NH4MgAs04 

Confirm  by  AgNO3,  forming  Test   for   Mo   by   KSCN  and 

red-brown  Ag,AsO4.  Zn  in  HC1.     Red  Mo(SCN)4. 


*  Browning,  Simpson  and  Porter,  Am.  Jour.  Sci.  XL,  349;  XLII,  106. 


224 


77/E 


ELEMENTS. 


r*a  j«rjfj 

Id*'!  Bill.. 
Illl  l2^Kf 


THE  QUALITATIVE  SEPARATION.  225 

V. 

THE  TUNGSTEN  GROUP. 

Before  taking  up  the  analysis  as  outlined  in  Table  VIII, 
the  student  is  instructed  to  review  the  reactions  of  the 
elements  considered. 

Taking  separate  solutions  of  the  following  salts,  Na2Sn03, 
Na2SiO3,  Na2WO4,  K8Ta6Oi9  and  K8Nb6O,9,  try  the 
action  of  the  following  reagents,  and  record  the  results 
in  tabular  form:  (i)  HN03  to  acid  reaction;  effect  of 
excess  and  result  on  evaporation;  (2)  HC1  and  H2SO4  under 
the  same  conditions  as  in  (i);  (3)  NaOH,  KOH  or  NH4OH 
upon  the  freshly  precipitated  oxide  or  hydroxide;  (4) 
Zn+HCl  on  solutions  of  Ta,  Nb,  and  W;  (5)  H2S  on 
solutions  containing  Ta,  Nb,  W,  Sn  and  Si,  and  subsequent 
acidification  with  HC1;  (6)  NaPO:<  bead  with  and  without 
FeSO4,  upon  small  particles  of  the  oxides  or  hydroxides. 
Try  also  the  effect  of  warming  the  dried  oxides  with  HP 
in  a  lead  dish. 

TABLE  VIII.* 


Dissolve  in  HF,  add  H2SO4,  and  evaporate  to  the  fuming-point  to  remove 
SiF4;  cool,  pour  into  5  cm.3  of  water,  add  NH4OH  to  alkaline  reaction,  then 
colorless  (NEL^S,  and  warm  in  a  covered  dish  at  60°  C.  for  15  minutes. 


Ta205,  Nb206,  (Ti02),  (WO,).  (NH4)2SnS3,  (NH4)2WS4. 

Warm  with  H2O2  and  HC1.  Acidify  with  HSSO4,  shake  and 

filter. 


Ta205.     Dissolve  in  HF, 
add   K2CO3,  and   boil. 
2K2TaF7,   Ta2O5  indi- 
cates Ta. 

[F 
NbCl5(Ti02)(WCl6). 
Evaporate  with  H2SO4, 
dilute,  pour  through 
a  Zn   column,   add 
HgCl2.    Ppt.Hg2Cl2 
indicates  Nb. 

R|                     |F 
SnS2.              H2WO4. 
(WS2).      Confirm        b  y 
Zn+HCl. 
Blue  color  indi- 
cates W. 

*  Abridged  and  adapted  from  A.  A.  Noyes,  Technology  Quarterly,  Vol.  XVII,  No. 
214. 


226  THE  R4RER  ELEMENTS. 

VI. 

THE  PLATINUM  GROUP. 

Before  attempting  any  separations  by  the  use  of  Table 
IX,  the  student  is  directed  to  review  the  reactions  of  the 
platinum  group. 

Take  separate  portions  of  solutions  of  H2PtCl6,  Na2IrCl6, 
K2OsCl6,  RuCl3,  Na3RhCl6,  and  PdCl2  and  try  the  action 
of  the  following  reagents  upon  them,  recording  the  results  in 
tabular  form:  (i)  H2S;  (2)  (NH4)2S  upon  the  sulphides 
precipitated;  (3)  KOH  or  NaOH;  (4)  KC1  or  NH4C1; 
(5)  KN02;  (6)  Na202;  (7)  Zn+HCl. 

The  separation  of  the  platinum  metals  is  one  of  the 
most  difficult  analytical  problems.  The  following  scheme, 
offered  by  Leidie  and  Quennessen  (Bull.  Soc.  Chim.  xxvn, 
181  (1902)),  has  been  found  to  give  fairly  satisfactory 
results  when  the  mixtures  examined  were  not  especially 
complex. 

TABLE  IX. 

The  finely  divided  metals  are  mixed  with  5  to  6  times  their  weight  of  Na202 
and  heated  gently  in  a  nickel  crucible.  Treat  with  water. 

R|—  —  |F 

The   residue    contains    Ni,    ^  c,  The  filtrate  contains  soluble  so- 

and  Rh,  as  insoluble  compounds.  dium  salts  of  Os,  Ru,  Ir,  and  Pd. 

Treat  with  hot  HC1,  filter,  evap-  Yellow  solution  =  Os,  Ru,  or  Pd. 

orate  excess  of  acid,  add  NaNO3  Blue  solution  =  Ir. 

and  NajCOa  to  neutrality,  and  Colorless  solution  =  absence  of  all. 

boil.  (a)  If  solution  is  yellow,  pass 

chlorine  and  heat,  catching  dis- 
dilate  in  cold  water. 

D 


Pl 

| 

Ni 


i  removed.    Add  excess  of 
HC1,  evapo- 

rate to  dry-     The  residue  when  (i)  If  either  Os  or  Ru  is 

ness.     Add          neutralized  with  present,  NH4SH  gives 

water     and          HC1  and  evap-  a  black  sulphide. 

NHUCl.  orated    with  (2)  If  Os  is  present  a 

_  NH4OH      and  violet  osmate  is  pro- 

Pi  |F  KC1  should  give  duced  by  KNO3and 

Pt  as  chloro-  Rh  in  solution  •       red    crystals   of  heating. 

platinate         as     reddish         potassium  chlor-  (3)  If  Ru  is  present   a 

double  chlo-         palladate  if  Pd  black   ppt.  of   Ru   is 

ride.  is     present.  produced    by     KOH 

and  alcohol  in  the  cold. 

(6)  If  solution     is    blue,  neutralize 

with  HCI,  evaporate  in  presence  of 

NH4OH  and  KC1.     Black  crystals 

of  potassium  chlor-iridate  =  Ir. 


SPECTROSCOPIC  TABLES.,  22J 


CHAPTER  XIV. 
SPECTROSCOPIC  TABLES. 

THE  importance  of  spectrum  analysis  in  the  chemistry 
of  the  rarer  elements  has  suggested  the  insertion  of  some 
spectroscopic  charts  and  tables. 

In  order  to  make  possible  the  location  with  a  fair  degree 
of  certainty  of  the  lines  in  the  field  of  visible  spectra, 
the  wave  lengths  of  the  Fraunhofer  lines  shown  in  spectrum 
No.  i,  on  the  chart  of  Flame  Spectra,  are  here  given: 

,4=7594;    5=6867.4;    ^  =  6563;    £  =  5893.1;    £  =  5270; 
6=5172;    £"=4861.4;     (7=4308;  H  =  3968. 6;  Hi  =3933.8.  ' 

A  comparison  of  these  lines  with  the  arbitrary  scale  given 
in  the  charts  of  Flame  and  Spark  Spectra  will  serve  to  locate 
the  position  of  the  various  spectra. 

In  the  table  of  Chief  Lines  only  a  few  of  the  more 
important  are  recorded.  The  figures  in  parenthesis,  e.  g. 
Li  (3232-6708),  show  the  range  of  the  chief  lines  as  given 
by  Exner  and  Haschek.  The  second  number,  (6),  gives 
the  total  number  of  chief  lines.  The  other  numbers, 
4202.2,  4603.1,  6103.8,  6708.1,  indicate  the  lines  of  greatest 
intensity.  Few  lines  of  an  intensity  below  10  on  the  scale 
used  by  these  investigators  are  mentioned,  and  those  in 
heavy  type  are  of  an  intensity  of  50  or  above. 

The  visible  spectrum  lies  between  7600  and  4000; 
the  lines  outside  of  these  limits,  non-existent  to  the  eye, 
are  observed  by  other  methods,  photography  being  espe- 
cially valuable  for  this  purpose  whenever  it  is  applicable. 
Many  of  the  principal  lines  of  the  rare  element  spectra  will 
be  seen  to  be  of  a  wave  length  below  4000,  _and  therefore 
to  lie  in  the  ultra  violet. 


228 


THE   RARER    ELEMENTS. 
TYPICAL  SPARK  SPECTRA. 


Beryllium,. 


20       30       40        50       60        7O       60       90       100       110       120      130       140       150       160 


Germanium. 


I      I      I      I   '   I   '   I      I      I      I      I      I      I 

20       30       40        50       60       70       80       90       100       110        120      130       140       150       160 


7ttan.Tu.m-. 


III!  III!  Illl  Mil 


20       30       40        50       60        70       60       90       100       110 


130       140       ISO       160 


Zircoruicm. 


20       30       40        50 


,'     I     '     I     '     I     '     I  .'  '  '     I     '     I 

70       80       90       100       110        120      130       140       150       160 


'     I     '     I     '     I     '     I     '     I     '    I     '     I    '     I    '     I     '         '     I     '     I     ' 

20        30       40        50       60        70       80        90       100       110       120      ISO       140       ISO       160 


I.  I  I      -I  I      '      I  I       -    I      '      I  I  I  I 

20       30        40        50       60        70       80       90       100       110        120       130       140       ISO       160 


li  i  ,.      r,    ,,  lit  (Hi,  I. 


Selenium,. 


'      I      '      I      '     I      '      I      '      I      '      I      '      |      '      I      '      I      '      I      '      I      '      I      '      I      '      . 
20       30       40        50       60        70       -80       90       100       110       120      130       140       ISO      160 


20       30       40        50       60       70 


90       100       110       120      130      140       150       160 


Selected  from  An  Introduction  to  the  Study  of  Spectrum  Analysis,  Watts. 
Longmans,  Green,  &  Co.  (1904). 


SPECTROSCOPIC  TABLES. 
TYPICAL  SPARK  SPECTRA. 


229 


Platinum,,  spark 


ii  i          i          i          i          i          i          I 

20       30       40        50       60        70       80       90       100       110       120      130       40       150 


HeUi 


,     .  .  .  .      |     i     |     .     |     •     |     .  I 

20       30       40       SO       60       70       80       90       100      110       120      130       140       150      !60 


w* 


30       4O       50       60       70       80       90       100       110       120      130       140       ISO      160 


ill  II  11  I    ,        ,lll     .    ,11111          Araon,.fN»») 


'     \     '     I     '     I     '     I     '     I     '         '     I     '     I  .  '     I     '     I     ' 
20       30       40       50       60       70       60       90      100      110       120      130      140      150 


JVeort. 


imiiiiiiiiiiiiimmiiimmiiiiiiiiiiiiiiiiiiiiiiii n iiiiiiiiiiimimimiiiiiiiiiiiiimmiiimimmiiiimHiiiiiii 


•    I    '    I    '    !    '    I    '    I    '    !    '    I    |    I    '    I       |   '   |   '   |   '   I   ' 

2O       30       40        60       60       7O       80       90       100       110       120      130      140      150      160 


iiiTlftinTifiHiii 


miiiinim 


Krypton,. 


20        30        40        50        60        70        80        90        100       110        120       I3O       140       150       160 

iii         HI      111  I   I    II    I  ll  I  i  n  Xenon. 


20        30        40        50        60        70        90        90       100       110        120       130       140       (50      160 


TYPICAL  ABSORPTION  SPECTRA. 


I.  Neodymium -Ammonium  Nitrate.  2.  Praseodymium-Ammonium  Nitrate. 

3.  Erbium  Chloride. 
From  Atlas  of  Absorption  Spectra,  by  Uhler  and  Wood,  Carnegie  Publication,  No.  71. 

230 


TYPICAL  ABSORPTION  SPECTRA. 


i.  Samarium  Chloride.     2.  Gadolinium  Chloride.     3.  Dysprosium  Chloride 
From  plates  accompanying  The  Absorption  Spectra  of  Solutions  of  Comparatively  Rare 
Salts,  by  Jones  and  Strong,  Carnegie  Publication,  No.  160. 

231 


232 


THE  RARER  ELEMENTS. 


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SPECTROSCOPIC    TABLES. 


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234 


THE  RARER  ELEMENTS. 


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1 1 


REVIEW  QUESTIONS. 


DESCRIPTIVE    PART. 

(In  answering  these  questions  be  prepared  tcT\vrite  equations  for  all  reactions.) 

I. 

LITHIUM,  RUBIDIUM,  CAESIUM. 

i.  (a)  Name  the  particulars  of  chemical  behavior  which  led  to  the 
discovery  of  Li.  (b)  How  and  under  what  circumstances  were  Rb  and 
Cs  discovered?  2.  Name  the  chief  mineral  sources.  3.  Are  these 
elements  found  elsewhere  than  in  minerals?  Give  examples.  4.  De- 
scribe in  full  the  method  you  employed  to  obtain  compounds  of  these 
elements  from  a  mineral  source.  5.  Discuss  briefly  two  other  methods 
of  extraction.  6.  How  are  the  elements  prepared  and  how  do  they 
compare  in  properties?  Compare  with  Na  and  K  in  elementary  con- 
dition. 7.  What  salts  are  soluble  in  alcohol?  8.  Name  two  important 
insoluble  salts  of  Li.  9.  Describe  the  action  of  SbCls,  SnCl4  and  PbCU 
upon  salts  of  Cs  and  Rb.  10.  What  happens  (a)  when  Na3Co(N02)8 
and  (b)  H2PtCl6  act  upon  solutions  of  Li,  Rb,  and  Cs  salts?  n.  Com- 
pare the  solubility  of  the  chloroplatinates  and  the  alums  of  Cs,  Rb  and 
K.  12.  Describe  the  flame  and  spectroscopic  tests  for  Cs,  Rb  and 
Li.  13.  Classify  the  alkalies  Li,  Na,  K,  Rb  and  Cs  into  two  groups 
and  give  reasons  for  the  classification, 

II. 
BERYLLIUM  AND   RADIO-ELEMENTS. 

I.  What  properties  of  the  compounds  of  Be  led  to  its  discovery? 
2.  Name  three  important  mineral  sources.  3.  How  did  you  obtain  a 
compound  of  Be  from  Beryl?  4.  Discuss  briefly  two  other  methods  of 
extraction.  5.  Discuss  briefly  the  preparation  and  properties  of  the 
element  Be.  6.  What  happens  when  a  solution  of  a  salt  of  Be  is  treated 
with  the  following  reagents:  (a)  NH4OH;  (b)  NaOH  or  KOH;  (c) 

235 


236  'THE  RARER   ELEMENTS. 

(NH4)2C03;  Na2C03  or  K2CO3;  (d)  Na2HP04.  7.  Discuss  the  behavior 
of  Be(OH)2  (a)  toward  NaHCO3;  (b)  toward  concentrated  solutions  of 
Be  salts.  8.  What  salts  of  Be  are  soluble  in  alcohol?  9.  Give  examples 
of  the  hydrolysis  of  Be  salts.  10.  Discuss  the  peculiarities  of  the  double 
alkali  tartrates  and  the  basic  acetates,  u.  Discuss  the  similarities 
and  differences  of  behavior  of  Be  and  Al  compounds.  12.  Name 
the  five  important  radio-elements.  13.  What  do  you  understand  by 
a,  /3  and  7  rays,  and  how  are  they  distinguished?  14.  State  briefly  the 
disintegration  theory.  15.  What  observations  led  to  the  discovery  of 
radium?  16.  What  are  the  chief  sources  of  radium?  17.  How  is  radium 
extracted  from  pitchblende  residues?  18.  What  common  element  does 
radium  resemble?  19.  Give  the  symbols  for  some  of  the  radium  salts. 
20.  Give  the  chief  chemical  characteristics  of  radium  salts.  21.  What 
are  some  of  the  physiological  effects? 

III. 
RARE  EARTHS    (YTTRIUM  AND    CERIUM   GROUPS). 

i.  Into  what  groups  are  the  rare  earths  classified  and  upon  what 
does  the  classification  depend?  2.  Name  five  of  the  most  important 
mineral  sources  of  the  rare  earths.  3.  What  are  the  chief  mineral 
sources  of  the  Y  group?  The  Ce  group?  4.  How  did  you  obtain  the 
oxalate  of  Y  from  gadolinite  and  the  oxalate  of  Ce  from  cerite?  5.  Dis- 
cuss the  preparation  and  properties  of  the  elements  Y  and  Ce.  6.  How 
do  the  following  reagents  act  upon  soluble  salts  of  Y  and  Ce:  NH4OH; 
Na2C03;  (NH4)2CO3;  NH4F;  Na2SO4  or  K2SO4  to  saturation;  KIO3; 
Na2HP04;  K4FeC«X6;  H2C2O4;  K2CrO4?  7.  Starting  with  Ce02 
show  how  you  would  form  CeCU  and  Ce(N03)4.  8.  How  does  H2Oa 
act  upon  cerous  salts  in  alkaline  solution,  and  upon  eerie  salts  in  acid 
solution?  9.  Discuss  the  reduction  of  eerie  salts  and  the  oxidation 
of  cerous  salts.  10.  Describe  a  delicate  test  for  Ce.  n.  How  did 
Mosander  separate  La  and  Di  from  Ce?  12.  How  did  Welsbach  separate 
Di  into  Pr  and  Nd?  13.  Name  three  of  the  cerium  earths  which  give 
absorption  spectra  and  show  by  a  rough  diagram  the  main  differences. 

14.  What  important  Y  earth  gives  a  distinct   absorption  spectrum? 

15.  What  is  the  marked  difference  between  Ce  and  the  other  Ce  earths? 

1 6.  How  would  you  separate  Ce  from  the  other  Ce  earths?     17.  Show 
by  a  diagram  the  order  of  the  discovery  of  the  Y  earths,  with  the  names 
of  the  discoverers,  the  dates  of  the  discoveries  and  the  sources  from 
which  the  earths  were  obtained.     Make  a  similar  diagram  for  the  Ce 
earths. 


REVIEW  QUESTIONS.  2   y 

IV. 
THORIUM  AND   ZIRCONIUM. 

i.  Name  the  chief  mineral  sources  of  Th  compounds.  2.  Name  the 
chief  mineral  source  of  Zr  compounds.  3.  How  may  Th02  be  prepared 
from  (a)  monazite?  (b)  mantle  ashes?  4.  How  did  you  obtain  a  Zr 
compound  from  zircon?  5.  Discuss  the  preparation  of  the  elements  Th 
and  Zr.  6.  Compare  the  action  of  the  following  reagents  upon  soluble 
salts  of  Th  and  Zr:  NH4OH;  NaOH;  (NH4)SCO,;  Na2C03;  Na2S04 
or  K2SO4  to  saturation;  Na2HPO4;  KF;  K4FeC6N6;  KIO3;  NasS203; 
H2C204;  (NH4)2C2O4  in  excess  and  the  addition  of  HC1  to  the  product; 
sebacic  acid.  7.  What  salt  of  Th  is  used  largely  commercially,  and  how 
is  it  used?  8.  In  what  reactions  does  Zr  resemble  and  in  what  differ 
from  the  rare  earths?  9.  What  happens  when  a  solution  of  a  Zr  salt  is 
treated  with  Na2HP04  in  the  presence  of  H202?  10.  What  happens 
when  a  solution  of  ZrCl4  is  shaken  with  ether? 

V. 
GALLIUM,  INDIUM,  THALLIUM. 

i.  What  are  the  chief  mineral  sources  of  Tl  compounds?  2.  In  what 
commercial  waste  product  is  Tl  often  found?  3.  Discuss  briefly  the 
method  for  the  extraction  of  Tl.  How  did  you  extract  it?  4.  Discuss 
the  preparation  and  properties  of  T1C1,  TIBr  and  TIL  5.  What  happens 
when  a  solution  of  a  thallous  salt  is  treated  with  (a)  H2PtG6,  (i) 
Na,Co(NO,)8>  (c)  K2Cr04,  (d)  H2S  and  (NH4)2S?  6.  Compare  Tl' 
•salts  with  Fb  salts  and  salts  of  the  alkalies.  7.  How  may  Tl'  salts  be 
oxidized?  8.  (a)  Compare  the  action  of  HC1  and  KOH  upon  solutions 
of  Tl'  and  Tl'"  salts;  (b)  What  happens  when  a  solution  of  TlCln  is 
shaken  with  ether?  9.  Show  how  Tl'"  salts  may  be  reduced.  10. 
Describe  the  flame  and  spectroscopic  tests  for  Tl.  n.  In  what  general 
class  of  minerals  are  Ga  and  In  found?  12.  Describe  the  methods 
briefly  by  which  they  may  be  separated  from  their  mineral  associates. 
How  did  you  identify  the  presence  of  In  in  a  residue  from  the  puri- 
fication of  Zn?  13.  Give  the  symbols  of  the  oxides,  chlorides,  nitrates, 
sulphates  and  alums.  14.  Discuss  the  similarities  between  Ga,  In  and 
Al.  15.  What  happens  when  a  solution  of  an  In  salt  is  boiled  with 
NH4HSO3?  16.  Describe  the  spectroscopic  test  for  In.  17.  What 
peculiar  physical  property  has  the  element  Ga? 


THE  RARER.  ELEMENTS. 

VI. 
TITANIUM  AND   GERMANIUM. 

i.  What  are  the  chief  mineral  sources  of  the  element  Ti?  2.  In  what 
animal  and  vegetable  products  has  Ti  been  found?  3.  Give  two  methods 
for  the  extraction  from  a  mineral  source.  4.  Discuss  the  preparation 
and  properties  of  the  element.  5.  Show  how  compounds  of  the  con- 
dition of  oxidation  represented  by  the  oxides  Ti2O3  and  Ti03  may  be 
obtained  from  Ti02.  6.  How  are  ortho-  and  metatitanic  acids  formed? 
7.  What  happens  (a)  when  a  solution  of  Ti  (804)2  is  treated  with  Na2HP04? 
(ft)  When  H2O2  is  added  before  the  Na2HP04?  (c)  When  Na2S03  is  added 
after  H202  and  Na2HPO4?  8.  Discuss  the  color  tests  for  Ti.  9.  What 
happens  when  a  solution  of  TiCl4  is  shaken  with  ether?  10.  Name  the 
chief  commercial  applications  of  Ti.  n.  What  led  Winkler  to  the  dis- 
covery of  Ge?  12.  What  are  the  chief  mineral  sources  of  the  element 
Ge?  13.  Give  briefly  the  method  of  extraction.  14.  Give  symbols  for 
some  of  the  chief  compounds.  15.  Discuss  similarities  between  Ge  and 
C,  Si,  and  Sn. 

VII. 

VANADIUM,  NIOBIUM  AND  TANTALUM. 

i.  What  are  the  chief  mineral  sources  of  V?  2.  How  would  you 
obtain  ammonium  vanadate  from  vanadinite?  3.  Discuss  the  formation 
of  sodium  vanadate  from  carnotite  (V02)2K2V208.  4.  How  may  V2O8 
be  obtained  from  ammonium  vanadate?  5.  Give  symbols  for  the  ortho-, 
meta-  and  pyrovanadates.  6.  Discuss  the  preparation  and  properties 
of  the  vanadates  of  Ag,  Pb  and  Ba.  7.  Give  symbols  for  the  oxides 
of  V  and  discuss  their  acidic  and  basic  character.  8.  Show  how  com- 
pounds of  V206  may  be  reduced,  and  how  compounds  of  V204  may  be 
oxidized.  9.  What  happens  when  an  alkaline  solution  of  a  vanadate 
is  saturated  with  H2S?  10.  What  are  some  of  the  important  commercial 
applications  of  the  element  V  and  of  its  compounds?  1 1.  Name  the  chief 
mineral  sources  of  the  elements  Nb  and  Ta.  12.  Discuss  the  decom- 
position of  Nb  and  Ta  minerals  by  potassium  bisulphate.  13.  Taking 
the  symbol  (Fe,Mn)(Nb,Ta)2C>6  as  that  of  columbite,  discuss  with 
equations  the  extraction  of  Nb  and  Ta.  14.  Discuss  the  preparation 
and  properties  of  the  elements.  15.  Show  how  by  the  action  of  KOH 
upon  Nb205  potassium  hexaniobate  may  be  formed,  and  how  by  the 
action  of  KOH  upon  Ta2Os  a  hexatantalate  and  a  metatantalate  may  be 
obtained.  16.  Discuss  any  differences  between  the  elements  Nb  and  Ta. 


REVIEW   QUESTIONS.  239 

17.  What  commercial  application  has  been  made  of  the  element  Ta? 

1 8.  What  evidence  have  we  that  Nb  and  Ta  exist  in  other  conditions  of 
oxidation  than  that  represented  by  the  oxides  Nb20s  and  TajOt? 


VIII. 
MOLYBDENUM,  TUNGSTEN,  URANIUM. 

i.  What  are  the  chief  mineral  sources  of  the  element  Mo?  2.  Describe 
a  process  for  the  preparation  of  MoO3  from  molybdenite.  3.  How  would 
you  obtain  the  same  oxide  from  wulfenite?  4.  Discuss  the  preparation 
and  properties  of  the  element.  5.  Name  the  chief  oxides  of  Mo  and 
classify  as  to  their  acid  or  basic  character.  6.  What  happens  when 
MoO3  is  treated  with  NH4OH  and  the  product  is  treated  with  a  solution 
of  a  Ba,  Pb  or  Ag  salt?  7.  Describe  the  action  of  H2S  upon  an  acidified 
solution  of  an  alkali  molybdate;  the  action  NH4OH+H2S  upon  a  solu- 
tion of  a  molybdate.  8.  Discuss  the  action  of  typical  reducing  agents 
upon  Mo  solutions.  9.  Describe  the  following  color  tests  for  Mo: 
(a)  H2SO4  cone.;  (b)  Zn+KSCN.  10.  What  commercial  applications 
have  been  made  of  Mo  and  its  compounds?  n.  What  are  the  chief 
mineral  sources  of  the  element  W?  12.  Describe  a  method  by  means 
of  which  you  obtained  W03  from  wolframite.  13.  What  happens  when 
W03  is  acted  upon  by  NH4OH,  KOH  or  NaOH.  14.  Starting 'with  the 
alkali  tungstates  show  how  tungstates  of  Ag,  Pb  and  Ba  may  be  formed. 
15.  Show  how  by  the  action  of  W03  upon  Na2WO4  a  metatungstate 
may  be.  formed.  16.  Discuss  the  action  of  H2S  and  NH4OH  upon 
tungstates,  and  the  action  of  acid  upon  the  sulphosalt.  17.  Give  symbols 
for  the  chief  oxides  of  W  and  some  of  the  salts  corresponding  to  the  con- 
ditions of  oxidation  represented.  18.  Describe  the  phenomena  accom- 
panying the  action  of  reducing  agents  upon  tungstates.  19.  Discuss 
preparation  and  properties  of  the  element  W.  20.  Discuss  the  impor- 
tant commercial  application  of  elementary  W  and  W  compounds.  21. 
What  are  the  chief  mineral  sources  of  the  element  U?  22.  How  did 
you  extract  U  salts  from  pitchblende?  From  carnotite?  23.  Discuss 
the  preparation  and  properties  of  the  element  U.  24.  What  happens 
(a)  when  a  uranyl  salt  (U02C12)  is  treated  with  KOH  or  NH4OH? 
Equations,  (b)  When  Na2O2+NaOH  are  added  to  a  salt  of  U.  25. 
How  does  (NH4)2C03  act  upon  the  uranates  of  Na,  K  or  NH?  26.  Dis- 
cuss the  action  of  Na2CO3,  (NH4)2S,  Na2HP04  and  K4FeC6N6  upon 
uranyl  salts.  27.  Discuss  the  color  reactions  of  uranyl  salts.  28.  Dis- 
cuss the  reduction  of  uranyl  salts  to  uranous  salts  and  the  oxidation  of 


240  THE  R4RER   ELEMENTS. 

uranous  salts  to  uranyl  salts.  29.  Discuss  the  differences  in  chemical 
behavior  between  uranyl  and  uranous  salts.  30.  To  what  commercial 
uses  has  U  been  applied? 

IX. 
SELENIUM   AND   TELLURIUM. 

i.  What  are  the  chief  mineral  sources  of  selenium  compounds? 
2.  In  what  commercial  residues  is  Se  often  found?  3.  Describe  two 
typic?!  processes  for  the  extraction  of  Se.  4.  How  did  you  prepare 
H2SeO3  from  Se?  5.  How  is  H2SeO4  prepared  from  Se  and  from  H2SeO3? 
6.  Discuss  the  preparation  and  properties  of  BaSeOs  and  BaSeO4.  7.  How 
is  H2SeO4  reduced  to  H2SeO3  and  H2SeO3  to  Se?  8.  Discuss  the  prepara- 
tion and  properties  of  H2Se  and  the  selenides.  9.  What  is  KSeCN, 
how  is  it  formed,  and  what  is  the  action  of  HC1  upon  it?  10.  Discuss 
the  preparation  and  properties  of  the  allotropic  forms  of  Se?  u.  How 
is  SeSOs  prepared  and  what  is  the  action  of  water  upon  it?  12.  To  what 
commercial  uses  has  Se  been  applied?  13.  What  observation  led  to  the 
discovery  of  Se?  14.  Discuss  the  behavior  of  Se  on  being  subjected 
to  heat.  15.  What  are  the  chief  mineral  sources  of  Te  compounds. 
1 6.  In  what  commercial  residues  is  Te  often  found?  17.  Describe  two 
typical  processes  for  the  extraction  of  Te.  18.  How  did  you  prepare 
TeOa  from  Te?  19.  How  did  you  prepare  K2TeO3  from  TeO2?  20. 
Discuss  the  preparation  of  H2Te04.  21.  How  is  TeCl4  formed,  and 
what  is  the  action  of  water  upon  it?  22.  How  is  TeI4  formed?  23. 
How  is  H2TeO4  reduced  to  H2TeO3?  24.  Discuss  with  equations  the 
preparation  of  the  basic  sulphate  and  nitrate  of  Te.  25.  How  did  you 
precipitate  the  element  Te?  26.  Discuss  the  action  of  KCN  upon  Te 
and  the  action  of  air  upon  the  product.  27.  What  happens  when 
strong  H2S04  acts  upon  Te,  and  when  the  product  is  treated  with 
water?  28.  What  is  the  behavior  of  Te  compounds  on  charcoal  before 
the  blowpipe?  29.  Discuss  the  preparation  and  properties  of  H2Te  and 
the  tellurides. 

X. 

PLATINUM  AND  THE  PLATINUM  METALS,  GOLD  AND  THE  RARE 
INERT   GASES   OF  THE  ATMOSPHERE. 

i.  In  what  forms  are  the  metals  of  the  Pt  group  generally  found  in 
nature?  Name  the  members  of  the  group.  2.  Name  a  mineral  source 
(a)  of  Pt,  (b)  of  Ru.  3.  Describe  (a)  a  fusion  process  and  (b)  a  wet  proc- 


REVIEW  QUESTIONS.  24I 

ess  by  which  Pt  alloys  may  be  attacked.  4.  Discuss  the  action  of  the 
acids  upon  Pt  and  the  Pt  metals.  5.  Which  of  the  Pt  group  of  metals 
has  the  lowest  and  which  the  highest  fusing  point?  6.  How  in  general 
may  the  metals  of  this  group  be  obtained  from  their  salts?  7.  Dis- 
cuss the  action  of  (a)  H2S,  (7>)  (NH4)2S,  (c)  NaOH  and  (d)  NH4C1  upon 
solutions  of  the  salts  of  the  Pt  metals,  e.g.,  chlorides.  8.  Mention  the 
technical  uses  to  which  Pt  and  the  Pt  metals  have  been  put.  9.  Show 
by  the  symbols  of  the  oxides  the  chief  conditions  of  oxidation  in  which 
Pt  and  the  Pt  metals  are  known.  10.  Discuss  the  occurrence  of  gold. 
ii.  Describe  briefly  six  methods  of  extraction.  12.  Discuss  the  chemi- 
cal and  physical  properties  of  the  metals.  13.  Name  the  two  con- 
ditions of  oxidation  and  give  symbols  for  the  oxides.  14.  What  hap- 
pens when  AuCls  is  acted  upon  by  the  following  reagents:  (a)  H2S, 
(6)  KI,  (c)  NH4OH,  (d)  SnCl2,  (e)  FeSO4,  (/)  H2C2O4,  (g)  KOH+H202. 
15.  Discuss  the  action  upon  metallic  gold  of  (a)  aqua  regia,  (b)  chlo- 
rine or  bromine,  (c)  potassium  cyanide.  16.  Discuss  briefly  the  obser- 
vations which  led  to  the  discovery  of  argon.  17.  Discuss  briefly  the 
observations  which  led  to  the  discovery  of  helium.  18.  How  were  kryp- 
ton, xenon  and  neon  discovered?  19.  Discuss  briefly  the  occurrence  of 
these  gases.  20.  Discuss  briefly  the  extraction.  21.  Make  a  compara- 
tive table  showing  the  density,  boiling  points  and  spectra  of  these  gases. 


ANALYTICAL  PART. 

I. 

Show  how  by  the  use  of  HN03,  HC1,  H2S,  NH4OH  successively  upon 
individual  solutions  of  salts  of  the  following  elements  they  may  be  clas- 
sified into  groups:  IT,  W,  Au,  Pt,  Te,  Se,  Mo,  Ge,  Ir,  Ru,  Rh,  Os,  Pd, 
V,  Ce,  Pr,  Nd,  Y,  Th,  Zr,  Be,  Ti,  Ta,  Nb,  Ga,  In,  Tl'",  U,  Li,  Rb,  Cs. 

II. 
TIN  AND   TUNGSTEN   GROUP. 

I.  What  happens  when  a  solution  containing  Ta,  Nb,  W,  Si  and  Sn 
is  evaporated  to  drynes^  with  HNOa?  2.  What  happens  when  the 
oxides  of  Ta,  Nb,  W,  Si  and  Sn  are  treated  with  HF  and  the  solution 
evaporated  to  the  fuming  point  with  H2S04?  3.  Discuss  the  action  of 
NH4OH+(NH4)2S  upon  the  residue  after  removal  of  SiO2.  4.  How 
does  a  mixture  H2O2  and  HC1  act  upon  Nb204  and  TaaOj?  5.  How 
do  we  detect  (a)  Ta  (6)  Nb?  (c)  W? 

III. 
HC1  GROUP. 

i.  What  rare  basic  ion  may  be  precipitated  from  a  nitric  acid  solution 
by  HC1?  2.  Is  T1C1  completely  precipitated  by  HC1?  How  shown? 
3.  How  do  we  separate  Tl  from  Hg2  and  Ag?  From  Pb?  4.  Which  is 
the  more  insoluble,  T1C1  or  Til?  5.  How  does  HC1  act  upon  solutions 
containing  Tl'"?  6.  What  oxidizing  agents  change  Tl'  to  Tl'"?  7. 
How  may  Tl"'  be  reduced  to  Tl'?  8.  Comment  upon  the  solubility 
of  T1C1  in  water  and  in  HC1.  9.  Comment  upon  the  solubility  of  Til 
in  water  and  in  KI. 

IV. 

H2S  GROUP. 

i.  Name  the  rarer  elements  which  are  precipitated  by  H2S  in  acid 
solution.  2.  Why  is  H2S  passed,  first  in  hot  strongly  acid,  and  then  in 

242 


REVIEW  QUESTIONS.  243 

cold  dilute  solution?  3.  Which  of  the  sulphides  are  best  precipitated 
under  gentle  pressure  and  how  is  this  accomplished?  4.  Which  of  the 
sulphides  are  dissolved  by  (NH4)2S?  5.  How  did  we  separate  Pt  from 
As,  Se,  Te,  Au  and  Mo?  6.  Why  is  K2PtCU  washed  with  KC1  rather 
than  with  water,  and  how  is  the  presence  of  Pt  confirmed?  7.  What 
happens  when  a  solution  containing  Au,  Se,  Te  and  Mo  is  warmed  with 
oxalic  acid?  8.  Why  is  oxalic  acid  used  rather  than  H2S03?  9.  What 
happens  when  a  solution  containing  Te  and  Se  is  strongly  acidified  with 
HC1  and  treated  with  Na2SO3?  10.  Why  is  KI  added  to  the  diluted 
solution  containing  Te  after  the  removal  of  the  Se?  n.  How  is  Mo 
detected  and  what  is  the  compound  formed?  12.  How  did  we  separate 
Pt  and  Au  from  the  residue  from  the  (NH4)2S  treatment? 


V. 
Pt  GROUP. 

i.  Name  the  metals  of  the  platinum  group.  2.  How  is  this  group 
subdivided  after  the  fusion  with  Na2O2?  3.  How  do  we  separate  Pt 
from  Rh?  4.  What  does  a  colorless  solution  after  the  extraction  of  the 
Na2O2  fusion  indicate? — a  blue  solution? — a  yellow  solution?  5.  How 
do  we  separate  Ru  and  Os  from  Ir  and  Pd?  6.  How  are  Ir  and  Pd 
detected?  7.  How  may  Ru  and  Os  be  detected  when  present  together? 


VI. 
NH4OH  AND    (NH4)2S   GROUP. 

i.  Name  the  rarer  elements,  exclusive  of  the  rare  earth  group,  which 
are  precipitated  by  (NH4)2S+NH4OH.  2.  How  may  these  elements 
be  divided  into  two  groups  by  the  action  of  NaOH+Na202+Na2C03? 
3.  What  happens  when  a  solution  of  the  chlorides  of  Ti,  Zr,  and  Tl  is 
shaken  with  ether?  4-  How  may  Tl  be  detected  in  the  presence  of  Fe? 
5.  How  did  you  separate  Zr  and  Ti?  6.  Why  are  H202  and  Na2S03 
used  in  the  separation  and  detection  of  Ti  as  the  phosphate?  7.  What 
happens  when  a  solution  containing  U,  V,  and  Be  is  treated  with  a  slight 
excess  of  NaHCO3  and  warmed  upon  a  steam  bath?  8.  How  may  Be 
and  Al  be  separated?  9.  How  did  we  separate  U  from  V  and  confirm 
its  presence?  10.  How  did  we  test  for  the  presence  of  V? 


244  TtfE  R^RER  ELEMENTS. 

VII. 
RARE   EARTH   GROUP. 

i.  At  what  point  in  the  analysis  are  the  rare  earths  precipitated? 
2.  What  is  the  action  of  HF  or  NH4F  upon  a  solution  containing  the  rare 
earths?  3.  How  may  the  rare  earths  and  alkali  earths  be  separated  if 
present  together  as  fluorides?  4.  Discuss  the  action  of  Na2S2O3  upon  a 
solution  containing  Ce,  Y  and  Th.  5.  How  may  the  presence  of  Th  be 
confirmed?  6.  What  happens  when  a  solution  containing  Ce  and  Y  is 
saturated  with  K2S04  or  Na^SCU?  7.  How  may  the  presence  of  Ce  be 
confirmed?  8.  How  did  we  test  for  Y?  9.  Discuss  briefly  a  method 
for  the  separation  of  the  other  members  of  the  Ce  group.  10.  Discuss 
the  separation  of  the  Y  group. 

VIII. 
ALKALI  GROUP. 

i.  What  happens  when  a  solution  of  the  chlorides  of  the  alkalies  is 
dehydrated  with  amyl  alcohol?  2.  How  do  we  confirm  the  presence  of 
Li?  3.  How  may  the  alkali  chlorides  be  converted  into  the  carbonates? 
4.  How  may  the  carbonate  of  Cs  be  separated  from  the  other  alkali 
carbonates?  5.  How  may  we  confirm  the  presence  of  Cs?  6.  How  may 
Rb  and  K  be  separated  from  Na?  7.  Suggest  a  method  for  the  separa- 
tion of  Rb  and  K.  8.  Describe  the  spectroscopic  tests  for  Na,  K,  Li, 
Cs,  and  Rb.  9.  How  may  the  alkali  salts  be  converted  into  sulphates? 
10.  How  may  the  sulphates  be  converted  into  carbonates? 


QUALITATIVE  DETECTION.  245 

Given  a  solution  which  may  contain  one  of  the  following  elements: 
Ta,  Nb,  W,  Tl1  or  m,  Au,  Pt,  Se,  Te,  Mo,  V,  U,  Zr,  Th,  Ce,  Y,  Ti,  Be, 
Cs,  Rb,  Li.  • 

A.  Add  HC1  to  acidity  but  not  in  large  excess.     Formation  of  a 
precipitate  indicates  Ta,  Nb,  W  or  Tl1.     (Note:  gentle  warming  makes 
H2WO4  more  insoluble;  H2Te03  may  be  precipitated  from  K2Te03,  but 
dissolves  in  excess.) 

If  the  precipitate  dissolves  on  warming,  Tl1  is  indicated.  Confirm 
by  other  tests  on  original  solution. 

If  Tl1  is  not  indicated,  add  a  piece  of  Zn  to  the  acidified  solution  and 
enough  HC1  to  insure  a  good  evolution  of  H2.  Blue  color  indicates  W. 
Violet  color  indicates  Nb.  Absence  of  color  indicates  Ta.  Confirm  if 
possible  by  other  tests  on  original  solution. 

B.  If  no  precipitate  appeared  on  addition  of  HC1,  add  H2S.     Brown/ 
to  black  indicates  Au,  Pt,  Te,  Mo;    yellow  to  red  indicates  Se.     White 
sulphur  with  blue  solution  indicates  V.     White  sulphur  with  colorless 
solution  indicates  Tlm.     Identify  by  following  tests  on  original  solution:. 
Au  by  FeS04  or  by  H202+NaOH= metallic  gold;    Pt  by  KI  =  reddish 
violet  color;    Te  by  SnCl2  =  black  Te;     Se  by  Na2S203+HCl  =  red  Se; 
Mo  by  Zn+HCl+KSCN  =  redMo(SCN)4;    V   by  NH4OH+H2S  =  red 
NH4VS3;   T1IU   by  NH4OH  =  brown  precipitate,   T1(OH)3.     Confirm  by 
all  possible  tests. 

C.  If  no  precipitate  occurs  with  H2S,  boil  out  H2S,  cool,  add  NH4OH 
to  alkaline  reaction.     Yellow  precipitate  indicates  U.     Brown  indicates 
Tlm.     White  indicates  Zr,  Th,  Ce,  Y,  Ti  or  Be.      If  the  precipitate  is 
white,  dissolve  in  least  possible  amount  of  HC1  and  add  H2C2O4.    White 
precipitate  indicates  Y,  Ce,  Th(Zr).     No  precipitate  indicates  Ti,  Be, 
Zr.     Identify  as  follows:    Ce  by  NaOH+H2O2= yellow-brown  Ce(OH)8. 
Th  by  solubility  of  oxalate  in  (NH4)2C2O4. ;   Y  by  negative  results  with 
last  two  tests;   Ti  by  yellow  to  red  color  with  H202;   Be  by  precipitate 
with  NaOH  soluble  in  excess;  Zr  by  negative  results  with  last  two  tests 
and  precipitation  with  Na2HP04.     Confirm  all  by  possible  tests,  including 
tests  for  U  and  Tl. 

D.  If  no  precipitate  was  formed  by  NH<OH,  treat  the  original  solu- 
tion with  Na3Co(N02)e;  a  precipitate  indicates  Cs  or  Rb.     No  precipitate 
indicates  Li.     Confirm  by  spectroscopic  and  flame  tests. 

NOTE.— Ge  gives  a  white  sulphide  with  HC1+H2S.  Ga  and  In  give 
white  precipitate  with  NH4C1+NH4OH.  Ga(OH)3  is  soluble,  In(OH)3  is 
insoluble  in  KCH;  In  salts  give  characteristic  flame  spectra. 


846 


THE  RARER  ELEMENTS. 


IS  | 


*X  | 


n| 


Off 


-«x  | 


A| 


JXJ_ 


"I  '*€>  | 


JZ| 


MX  | 


n\ 


T 


I      I      I      I      I      I 


Lid. 


I  I 


I  I  I 


I 

•v|     I     I 

POl 


I      I      I 

J_1_L 
I   I 


I   I   1*1   I   I   I   1*1 


1   I   I   I 


II   I    I    I 


I   M   I   I   I 


I    I    I* 
MM 


I    I 


!    I 


I   I   I   1*1*1 


I   1*1' 


BV| 


ARC  SPECTRA  OF  SOME  GALLIUM  AND  INDIUM  PRODUCTS.   247 


2       42 


MINERALS  AND  REAGENTS  USED  IN  THE  STUDY 
OF  THE  RARER  ELEMENTS. 

A.  Minerals   and   Commercial   Residues   from  which   the 

Rarer  Elements  are  extracted : 

Li,  Lithiophilite ;  Cs  and  Rb,  Lepidolite;  Be,  Beryl; 
Ce,  Cerite  or  Monazite  Residues  from  the  extraction 
of  Thorium;  Y,  Gadolinite;  Th,  Monazite  or  Wels- 
bach  Mantle  Ash;  Zr,  Zircon;  Ga  and  In,  Leady 
Residue  from  the  Purification  of  Zinc;  Tl,  Flue 
Dust;  Ti,  Rutile  or  Illmenite;  Ge,  Germaniferous 
Zinc  Oxide;  V,  Carnotite  or  Patronite;  Cb  (Nb)  and 
Ta,  Columbite;  Mo,  Molybdenite;  W,  Wolframite 
or  Hiibnerite;  U,  Pitchblende  or  Carnotite;  Se  and 
Te,  Copper  Refining  Residues;  Pt,  Platinum  Resi- 
dues; Au,  Gold  Ore. 

B.  Reagents: 

Acids — Sulphuric,  Hydrochloric,  Nitric,  Acetic,  Oxalic, 
Orthophosphoric,  Tartaric,  Sebacic,  Tannic,  Gallic, 
Pyrogallic,  Chloroplatinic. 

Ammonium  Compounds — Hydroxide,  Carbonate,  Chlor- 
ide, Sulphide,  Acetate,  Oxalate,  Acid  Sulphite, 
Sodium  Hydrogen  Phosphate,  Alum. 

Sodium  Compounds — Hydroxide,  Carbonate,  Acid  Car- 
bonate, Sulphate,  Sulphite,  Thiosulphate,  Fluoride, 
Hypochlorite,  Hydrogen  Phosphate,  Dioxide,  Co- 
balti-Nitrite. 

Potassium  Compounds — Hydroxide,  Bromide,  Iodide, 
Sulphate,  Ferrocyanide,  Cyanide,  Ferricyanide, 
Chloride,  Acid  Sulphate,  Nitrite,  lodate,  Formate, 
Sulphocyanide,  Chromate,  Carbonate,  Perman- 
ganate. 

249 


250  THE   RARER   ELEMENTS, 

Aluminum  Sulphate,  Antimony  Trichloride,  Barium 
Carbonate,  Barium  Chloride,  Bromine  Water,  Cal- 
cium Fluoride,  Copper  Sulphate,  Ferrous  Sulphate, 
Ferric  Chloride,  Hydrogen  Dioxide,  Lead  Acetate, 
Lead  Dioxide,  Magnesium,  Mercurous  Nitrate,  Stan- 
nous  Chloride,  Stannic  Chloride,  Silver  Nitrate. 

Amyl  Alcohol,  Ethyl  Alcohol,  Carbon  Bisulphide,  Char- 
coal, Starch,  Asbestos  Fibers,  Litmus  Paper,  Tur- 
meric Paper. 

Generators — Hydrogen  Sulphide,  Carbon  Dioxide,  Hy- 
drochloric Acid,  Chlorine. 

Special  Organic  Reagents — Diphenylcarbazid,  Hydra- 
zine  Sulphate,  Morphia,  Nitroso-beta-naphthol, 
Phenylhydrazin,  Thiourea. 

Compounds  of  the  Rarer  Elements  which  it  is  desirable 
to  have  on  hand : 

Nitrates  or  Chlorides  of  Li,  Cs,  Rb,  Be,  Y,  Ce,  La,  Pr, 
Nd,  Th,  Zr. 

Chlorides  of  Au,  Pt,  Pd,  Ru. 

Nitrates  of  Tl,  U. 

Oxides:    Ti02,  Nb2O5,  Ta2O5,  Mo03,  WO3,  SeO2,  Te02. 

Ammonium  Vanadate,  Sodium  Rhodium  Chloride,  So- 
dium Iridium  Chloride,  Potassium  Osmium  Chloride. 

Apparatus. 

A  set  of  apparatus  which  would  be  issued  for  a  course  in 
Qualitative  Analysis  would  cover  the  needs  of  this  course. 
A  spectroscope  or  two  should  be  on  hand  for  observation  of 
flame  and  absorption  spectra. 


PUBLISHED  WORKS   OF   PHILIP  E.  BROWNING. 

Journal  Articles 

1.  A  Method  for  the  Determination  of  Iodine  in  Haloid  Salts. 

(1890);  by  F.  A.  Gooch  and  P.  E.  Browning.  Amer.  Jour. 
Sci.,  XXXIX,  188. 

2.  A  Method  for  the  Reduction  of  Arsenic  Acid  in  Analysis  (1890); 

by  F.  A.  Gooch  and  P.  E.  Browning.  Amer.  Jour.  Sci., 
XL,  66. 

3.  Analysis  of  Rhodochrosite  from  Franklin  Furnace,  New  Jersey 

(1890);  by  P.  E.  Browning.     Amer.  Jour.  Sci.,  XL,  395. 

4.  A  Method  for  the  Quantitative  Separation  of  Strontium  from 

Calcium  by  the  Action  of  Amyl  Alcohol  on  the  Nitrates 
(1892);  by  P.  E.  Browning.  Amer.  Jour.  Sci.,  XLIII,  50. 

5.  A   Method   for   the   Quantitative   Separation   of   Barium   from 

Calcium  by  the  Action  of  Amyl  Alcohol  on  the  Nitrates 
(1892);  by  P.  E.  Browning.  Amer.  Jour.  Sci.,  XLIII,  315. 

6.  On  the  Qualitative  Separation  and  Detection  of  Strontium  and 

Calcium  by  the  Action  of  Amyl  Alcohol  on  the  Nitrates 
(1892);  by  P.  E.  Browning.  Amer.  Jour.  Sci.,  XLIII,  386. 

7.  A   Method   for   the   Quantitative   Separation   of   Barium   from 

Strontium  by  the  Action  of  Amyl  Alcohol  on  the  Bromides 
(1892);  by  Philip  E.  Browning.  Amer.  Jour.  Sci.,  XLIV, 

459- 

8.  A  Note  on  the  Method  for  the  Quantitative  Separation  of  Stron- 

tium from  Calcium  by  the  Action  of  Amyl  Alcohol  on  the 
Nitrates  (1892);  by  Philip  E.  Browning.  Amer.  Jour.  Sci., 
XLIV,  462. 

9.  On  the  Determination  of  Iodine  in  Haloid  Salts  by  the  Action 

of  Arsenic  Acid  (1893);  by  F.  A.  Gooch  and  P.  E.  Browning. 
Amer.  Jour.  Sci.,  XLV,  334;  Trans.,  Zeit.  Anorg.  Chem., 
IV,  178. 

10.  The  Influence  of  Free  Nitric  Acid  and  Aqua  Regia  on  the  Pre- 
cipitation of  Barium  as  the  Sulphate  (1893);  by  Philip  E. 
Browning.  Amer.  Jour.  Sci.,  XLV,  399. 

251 


252  THE  RARER  ELEMENTS. 

11.  On  the  Separation  of  Copper  from  Cadmium  by  the  Iodide 

Method  (1893);  by  Philip  E.  Browning.  Amer.  Jour.  Sci., 
XLVI,  280. 

12.  Reduction  der  Vanadinsaure  durch  Einwirkung  von  Weinsaure 

und  Titration  derselben  in  Alkalischer  Losung  durch  lod. 
(1894);  von  P.  E.  Browning.  Zeit.  Anorg.  Chem.,  VII,  158. 

13.  On  the  Interaction  of  Chromic  and  Arsenious  Acids   (1896); 

by  Philip  E.  Browning.    Amer.  Jour.  Sci.,  IV,  I,  35. 

14.  On  the  Reduction  of  Vanadic  Acid  by  Hydriodic  and  Hydro- 

bromic  Acids,  and  the  Volumetric  Estimation  of  the  same 
by  Titration  in  Alkaline  Solution  with  Iodine  (1896);  by 
Philip  E.  Browning.  Amer.  Jour.  Sci.,  IV,  185;  Trans., 
Zeit.  Anorg.  Chem.,  XIII,  113. 

15.  On  the  Estimation  of  Cadmium  as  the  Oxide  (1896);  by  Philip 

E.  Browning  and  Louis  C.  Jones.  Amer.  Jour.  Sci.,  II,  269; 
Trans.,  Zeit.  Anorg.  Chem.,  XIII,  no. 

1 6.  On  the  Application  of  Certain  Organic  Acids  to  the  Estimation 

of  Vanadium  (1897);  by  Philip  E.  Browning  and  Richard 
T.  Goodman.  Amer.  Jour.  Sci.,  II,  355;  Trans.,  Zeit. 
Anorg.  Chem.,  XIII,  427. 

17.  On  the  Detection  of  Sulphides,  Sulphates,  Sulphites,  and  Thio- 

sulphates  in  the  Presence  of  Each  Other  (1898);  by  Philip 
E.  Browning  and  Ernest  Howe.  Amer.  Jour.  Sci.,  VI,  317; 
Trans.,  Zeit.  Anorg.  Chem.,  XVIII,  371. 

18.  On  the  Volumetric  Estimation  of  Cerium  (1899);   by  Philip  E. 

Browning,  with  G.  A.  Hanford,  F.  T.  Hall,  Wm.  D.  Cutter 
and  Leo  A.  Lynch.  Amer.  Jour.  Sci.,  VIII,  451;  Trans., 
Zeit  Anorg.  Chem.,  XXII,  297. 

19.  On  the  Estimation  of  Thallium  as  the  Chromate  (1899);    by 

Philip  E.  Browning  and  George  P.  Hutchins,  Amer.  Jour. 
Sci.,  VIII,  460;  Trans.,  Zeit.  Anorg.  Chem.,  XXII,  380. 

20.  On  the  Estimation  of  Thallium  as  the  Acid  and  Neutral  Sul- 

phates (1900);  by  Philip  E.  Browning.  Amer.  Jour.  Sci., 
LX,  137;  Trans.,  Zeit.  Anorg.  Chem.,  XXIII,  155. 

21.  On  the  Qualitative  Separation  of  Nickel  from  Cobalt  by  the 

Action  of  Ammonium  Hydroxide  on  the  Ferricyanides 
(1900);  by  Philip  E.  Browning  and  John  B.  Hartwell. 
Amer.  Jour.  Sci.,  X,  315;  Trans.,  Zeit.  Anorg.  Chem.,  XXV, 
323- 


PUBLISHED  WORKS  OF  PHILIP  E.  BROWNING.  253 

22.  On  the  Estimation-  of  Caesium  and  Rubidium  as  the  Acid  Sul- 

phates, and  of  Potassium  and  Sodium  as  the  Pyrosulphates 
(1901);  by  Philip  E.  Browning.  Amer.  Jour.  Sci.,  XII,  301; 
Trans.,  Zeit,  Anorg.  Chem.,  XXIX,  140. 

23.  On  Ceric  Chromate  (1903);  by  Philip  E.  Browning  and  Charles 

P.  Flora.    Amer.  Jour.  Sci.,  XV,  177. 

24.  On  the  Arsenate  Process  for  the  Separation  of  Magnesium  from 

the  Alkalies  (1907);  by  Philip  E.  Browning  and  W.  A. 
Drushel.  Amer.  Jour.  Sci.,  XXIII,  293;  Trans.,  Zeit.  Anorg. 
Chem.,  LIV,  141. 

25.  A   Method  for   the  Qualitative   Separation  and   Detection  of 

Ferrocyanides,  Ferricyanides  and  Sulphocyanides  (1907); 
by  P.  E.  Browning  and  H.  E.  Palmer.  Amer.  Jour.  Sci., 
XXIII,  448;  Trans.,  Zeit.  Anorg.  Chem.,  LIV,  315. 

26.  The    Increasing    Importance    of    the    Rarer    Elements    (1908). 

Science,  XXVIII,  pp.  548-555- 

27.  On  the  Estimation  of  Cerium  in  the  Presence  of  the  Other  Rare 

Earths  by  the  Action  of  Potassium  Ferricyanide  (1908); 
by  Philip  E.  Browning  and  Howard  E.  Palmer.  Amer. 
Jour.  Sci.,  XXVI,  83;  Trans.,  Zeit.  Anorg.  Chem.,  LIX, 

7i- 

28.  The  Volumetric  and   Gravimetric  Estimation  of  Thallium  in 

Alkaline  Solution  by  Means  of  Potassium  Ferricyanide 
(1909);  by  Philip  E.  Browning  and  Howard  E.  Palmer. 
Amer.  Jour.  Sci.,  XXVII,  379;  Trans.,  Zeit.  Anorg.  Chem., 
LXII,  218. 

29.  The  Quantitative  Precipitation  of  Tellurium  Dioxide  and  its 

Application  to  the  Separation  of  Tellurium  from  Selenium 
(1909);  by  Philip  E.  Browning  and  William  R.  Flint. 
Amer.  Jour.  Sci.,  XXVIII,  112;  Trans.,  Zeit.  Anorg.  Chem., 
LXIV,  104. 

30.  The  Complexity  of  Tellurium  (1909);  by  Philip  E.  Browning  and 

William  R.  Flint.  Amer.  Jour  Sci.,  XXVIII,  347;  Trans., 
Zeit.  Anorg.  Chem.,  LXIV,  112. 

31.  On  the  Substitution  of  Bromine  and  of  Iodine  for  Chlorine  in 

the  Separation  of  Cerium  from  the  Other  Cerium  Earths 
(1910);  by  Philip  E.  Browning  and  Edwin  J.  Roberts. 
Amer.  Jour.  Sci.,  XXIX,  45;  Trans.,  Zeit.  Anorg.  Chem., 
LXXI,  305,  LXIV,  302.  . 


254  THE  RARER    ELEMENTS. 

32.  The  Gravimetric  Estimation  of  Vanadium  as  Silver  Vanadate 

(1910) ;  by  Philip  E.  Browning  and  Howard  E. Palmer.  Amer. 
Jour. Sci., XXX,  220;  Trans., Zeit.  Anorg.  Chem.,LXVIII,  263. 

33.  On  the  Decomposition  of  the  Cerium  Earth  Double  Sulphates 

with  the  Alkali  Sulphates  by  Fusion  with  Charcoal  (1911); 
by  Philip  E.  Browning  and  Philip  L.  Blumenthal.  Amer. 
Jour.  Sci.  (4),  XXXII,  164. 

34.  On  the  Qualitative  Detection  of  Certain  Elements  which  form 

Insoluble  Sulphates;  Barium,  Strontium  (Calcium),  and 
Lead  (1911);  by  Philip  E.  Browning  and  Philip  L.  Blumen- 
thal. Amer.  Jour.  Sci.  (4),  XXXII,  246. 

35.  A  Modified  Procedure  for  the  Detection  of  Silicates,  Fluorides 

and  Fluosilicates  (1911);  by  Philip  E.  Browning.  Amer. 
Jour.  Sci.  (4),  XXXII,  249. 

36.  The  Conservation  of  Phosphates  in  the  Urine  (1912);  by  Philip 

E.  Browning.  Original  Communications,  Eighth  Interna- 
tional Congress  of  Applied  Chemistry,  XV,  41. 

37.  On  the  Effect  of  Free  Chlorine  upon  the  Product  of  Hydrolysis 

of  Tellurous  Chloride  (1912);  by  Philip  E.  Browning  and 
George  O.  Oberhelman.  Original  Communications,  Eighth 
International  Congress  of  Applied  Chemistry,  XV,  59. 

38.  On  the  Detection  and  Separation  of  Aluminium  and  Beryllium 

by  the  Action  of  Amyl  Alcohol  on  the  Nitrates  (1912);  by 
Philip  E.  Browning  and  Simon  B.  Kuzirian.  Original 
Communications,  Eighth  International  Congress  of  Applied 
Chemistry,  XV,  87. 

39.  Preparation  of  Telluric  Acid  and  Test  for  Associated  Tellurous 

Acid  (1913);  by  Philip  E.  Browning  and  H.  D.  Minnig. 
Amer.  Jour.  Sci.,  XXXVI,  72;  Trans.,  Zeit.  Anorg.  Chem., 
LXXXIV,  227. 

40.  Preparation  of  Tellurous  Acid  and  Copper  Ammonium  Tellurite 

(1913);  by  G.  C.  Oberhelman  and  Philip  E.  Browning. 
Amer.  Jour.  Sci.,  XXXVI,  399. 

41.  Action  du  Brome  sur  les  Hydroxydes  de  Lanthane  et  des  Didy- 

mes  (1914);  by  Philip  E.  Browning.  Comptes  rend,  de 
Pacad.  d.  sciences,  CLVIII,  1679. 

42.  A  Note  on  the  Qualitative  Detection  and  Separation  of  Platinum, 

Arsenic,  Gold,  Selenium,  Tellurium  and  Molybdenum; 
by  Philip  E.  Browning.  Amer.  Jour.  Sci.,  XL,  349. 


PUBLISHED  WORKS  OF  PHILIP  E.  BROWNING. 


255 


43-  On  Two  Burners  for  the  Demonstration  and  Study  of  Flame 
Spectra  (1915);  by  Philip  E.  Browning.  Amer.  Jour.  ScL, 
XL,  507. 

44.  On  a  Gallium-Indium  Alloy  (1916);  by  Philip  E.  Browning  and 

H.  S.  Uhler.    Amer.  Jour.  Sci.,  XLI,  351. 

45.  On  the  Qualitative  Detection  and  Separation  (i)  of  Tellurium 

and  Arsenic  and  (2)  of  Iron,  Thallium,  Zirconium  and 
Titanium  (1916);  by  Philip  E.  Browning,  George  S.  Simpson 
and  Lyman  E.  Porter.  Amer.  Jour.  Sci.,  XLII,  106. 

46.  On  the  Separation  of  Caesium  and  Rubidium  by  the  Fractional 

Crystallization  of  the  Aluminium  and  Iron  Alums,  and  its 
Application  to  the  Extraction  of  these  Elements  from 
their  Mineral  Sources  (1916);  by  Philip  E.  Browning  and 
S.  R.  Spencer.  Amer.  Jour.  Sci.,  XLII,  279. 

47.  On  the  Electrolysis  and  Purification  of  Gallium  (1916);  by  H.  S. 

Uhler  and  Philip  E.  Browning.    Amer.  Jour.  Sci.,  XLII,  389. 

48.  On  the  Fertilizing  Value  of  Household  Wastes  (1917);  by  Philip 

E.  Browning.  N.  H.  Journal-Courier,  April  n,  1917; 
Jour,  of  Ind.  and  Eng.  Chem.,  IX,  1043. 

49.  On  the  Qualitative  Separation  and  Detection  of  Gallium  (1917); 

by  Philip  E.  Browning  and  Lyman  E.  Porter.  Amer.  Jour. 
Sci.,  XLIV,  221. 

.50.  On  the  Qualitative  Detection  of  Germanium  and  Its  Separation 
from  Arsenic  (1917);  by  Philip  E.  Browning  and  Sewell  E. 
Scott.  Amer.  Jour.  Sci.,  XLIV,  313. 

51.  Caesium,  Rubidium  and  Thallium  (1917);  by  Philip  E.  Browning. 

Mineral  Foote-Notes,  July,  1917. 

52.  Indium,  Gallium,  Germanium  (1917);    by  Philip  E.  Browning. 

Mineral  Foote-Notes,  September,  1917. 
•53.  Technical  Uses  of  the  Rarer  Elements   (1917);    by  Philip  E. 

Browning.     Mineral  Foote-Notes,  September,  1917. 
.54.  On  the  Separation  of  Germanium  from  Arsenic  by  the  Distillation 

of  the  Chloride  in  the  Presence  of  a  Chromate  (1918);  by 

Philip  E.  Browning  and  Sewell  E.  Scott.    Amer.  Jour.  Sci., 

XLVI,  663. 


INDEX. 


Dis- 
covery 
and 
Occur- 
rence. 

Extrac- 
tion 
from 
Sources. 

Element 
and 
Com- 
pounds. 

Estima- 
tion 
and 
Separa- 
tion. 

Experi- 
mental 
Work. 

Spec- 
trum. 

Tech- 
nical 
Appli- 
cation. 

Actinium  

34 

34 

34 

Aldebaranium,    see    Lute- 

cium. 

Argon  
Beryllium  

191 

17 

193 

18 

195 
19 

21,  2IO 

22 

229,  195 

21,  228 

197 

Canadium 

232 

Caesium  
Cassiopeium,  see  Xeoytter- 

9 

9 

IO,   II 

12,13,209 

14 

16,  232 

bium. 

Celtium  

45.  52 

Cerium. 

56 

3Si  45.  5o 

57 

58,  59, 

215,216, 

218 

232 

J97 

Columbium,  see  Niobium  . 

Decipium  

62 

Dysprosium  

45,  51,  52 

45,  53 

54.  216 

218 

231,  232 

Erbium  

45,  51.  52 

45,  53 

53 

54.216 

218 

230,  232 

197 

Erythronium  

107 

Europium  

45,  54,55 

45,  55 

55 

55,  56 

216,  218 

232 

Gadolinium 

-   1 

218 

231,  232 

197 

Gallium  

83 

84 

840,  846 

846 

88 

232,  247 

Germanium  

105,  106 

1  06 

1060 

1066 

228,  232 

Glucinum,  see  Beryllium.  . 

Gold. 

183 

184 

186 

188     222 

TQn 

206 

Helium  

192 

194 

IO9 

232 

45,51,  52 

S3 

54,  216 

22    ,   195 

218 

Indium  

84& 

85 

86 

88 

88 

232,88 

Ionium. 

3O 

30 

Indium  

170 

162 

*73.  *75 

166,  226 

180 

232 

205 

Krypton  

191 

194 

195 

228,  195 

Lanthanum  

36,  45 

63 

63.64 

65,  216 

6l.  62 

218 

67 

232 

197 

Lithium. 

I 

2 

3 

4,  209 

£ 

6,  233 

197 

Lutecium  

45,  52 

233 

Menachite  

97 

126 

Monium,  see  Victorium. 

125 

Neodymium  

36,45, 

63 

63,64 

65,  216 

61.  62 

218 

67 

230.  233 

197 

257 


258 


INDEX. 


Dis- 
covery 
and 
Occur- 
rence. 

Extrac- 
tion 
from 
Sources. 

Element 
and 
Com- 
pounds. 

Estima- 
tion 
and 
Separa- 
tion. 

Experi- 
mental 
Work. 

Spec- 
trum. 

Tech- 
nical 
Appli- 
cation. 

Neon 

192 

196 

Niobium  
Ochroite,  see  Cerium  

116,  117 
56 
170 

no 

162 

119,  121 

122,  225 

166,  226 

123 

181 

233 

202 

205 

Palladium  
Platinum  

Polonium  

170 
161 

27,  34 

162 
162 

34 

172,  175 
162,  163 

34 

166,  226 

l6S,  222 
226 

180 
169 

228,  233 
228,  233 

20S 

205 

Praseodymium  

Radio-elements,  see  Chap. 
III. 
Radium  
Rare  earths,  see  Chap.  IV. 

36,  45. 
61,62 

30 

170 

63 

31 
162 

63 

32 

65,  216 
218 

168   226 

67 
182 

230,  233 

197 
206 

Rubidium    

6 

Ruthenium  

170 

162 
63 

174.  175 
63 

168,  226 
65   66 

182 

233 

206 

Scandium  

42,  62 

63 

63 

216,  218 
65,  216 

218 

231.  234 
234.  42 

197 

222 

Tellurium  
Terbium  

152 
45,51,  54 

153 
53 

154.  155 

55 

156,   157 
222 

55,  216 
218 

158 

228,  234 
234 

205 

36,  71 

71 

213,  222 

94 

56,  234 

199 

Thulium  

45.  51.  52 

53 

216 
54.  216 
218 

74 

234 
234 

198 

213 

103 

228,  234 

200 

138 

Vanadium  

Victorium  
Xenon  
Ytterbium,  see  Lutecium. 
Neoytterbium  

Yttrium  

107 

52 

192 

45.  52 

36 
45,  46,51 
36   76 

108 

154 
53 
46 

109.  no 

195 
53 

47 
77    78 

211 

in,  113 

213 

54.  216 
218 
49,  215 

2l6,  2lfi 

114 

49 
80 

228,  234 
228,  196 

234 

201 

198 
198 

This  book  is  DUE  on  the  last  date  stamped  below 


APR  7       193& 
APR  17   li 


Ij  1938 
"»te 


WAY  29  19H 


OCT  6 

JUl  22 
SEP  10 


194J 


Form  L-9-35»i-8,'28 


KC*D  LD-URl 

URL     MAY  181973 
MAY181973 


